Does TBird have a built-in limit on recipients?

[Restorm]

I'm involved in some big global projects, where I sometimes have to
respond to emails that have 150-200 recipients. When I reply to them, I
get an error message saying that there are too many recipients. My ISP
says their limit is set at 200, so they are wondering if the limit is in
my email client. Anyone know if Thunderbird has such a limit?

[Jay Garcia]

On 04.09.2012 09:27, Restorm wrote:

Not that I am aware of. Try sending in two batches.

--
Jay Garcia - www.ufaq.org - Netscape - Firefox - SeaMonkey - Thunderbird
Mozilla Contribute Coordinator Team - www.mozilla.org/contribute/
Mozilla Mozillian Member - www.mozillians.org
Mozilla Contributor Member - www.mozilla.org/credits/

[Ron K.]

Jay Garcia on 9/4/2012 10:46 AM, keyboarded a reply:

> On 04.09.2012 09:27, Restorm wrote:
>
> --- Original Message ---
>
>> I'm involved in some big global projects, where I sometimes have to
>> respond to emails that have 150-200 recipients. When I reply to them, I
>> get an error message saying that there are too many recipients. My ISP
>> says their limit is set at 200, so they are wondering if the limit is in
>> my email client. Anyone know if Thunderbird has such a limit?
>
> Not that I am aware of. Try sending in two batches.
>

Authenticate all the recipient addresses, that they are all valid. We
have seen similar user issues here over the years where a single bad
address causes the entire batch send to abort. Breaking the list down to
smaller batches may aid finding the one causing a problem.

--
Ron K.
Who is General Failure, and why is he searching my HDD?
Kernel Restore reported Major Error used BSOD to msg the enemy!

[clay]

On 09/04/2012 12:53 PM, Ron K. wrote:
> Jay Garcia on 9/4/2012 10:46 AM, keyboarded a reply:
>> On 04.09.2012 09:27, Restorm wrote:
>>
>> --- Original Message ---
>>
>>> I'm involved in some big global projects, where I sometimes have to
>>> respond to emails that have 150-200 recipients. When I reply to them, I
>>> get an error message saying that there are too many recipients. My ISP
>>> says their limit is set at 200, so they are wondering if the limit is in
>>> my email client. Anyone know if Thunderbird has such a limit?
>>
>> Not that I am aware of. Try sending in two batches.
>>
>
> Authenticate all the recipient addresses, that they are all valid. We
> have seen similar user issues here over the years where a single bad
> address causes the entire batch send to abort. Breaking the list down to
> smaller batches may aid finding the one causing a problem.
>

Both you guys missed the part where the OP states they are *replying* to
an email.
Be rather difficult to sort through, redistribute, or verify address's
in a reply...

[Chris Ramsden]

From: clay <c...@ymation.com>
Date: Tue 04 Sep 2012 21:28
To: support-t...@lists.mozilla.org
Subject: Re: Does TBird have a built-in limit on recipients?

> _______________________________________________
> support-thunderbird mailing list
> support-t...@lists.mozilla.org
> https://lists.mozilla.org/listinfo/support-thunderbird
> To unsubscribe, send an email to support-thund...@lists.mozilla.org?subject=unsubscribe
>
This site:

http://kb.mozillazine.org/Limits_%28Thunderbird%29

...says:

"E-mail addresses

There appears to be a limit of approximately 60 addresses when sending
messages if you enter each address separately. However, if you use lists
(mail distribution lists) for most of the addresses any limit is imposed
by whatever SMTP server you use.

You can receive messages sent to multiple addresses in the same mailbox.
Any limitations would be due to your e-mail provider."

If you don't know, don't guess.

Grrr.

[Beauregard T. Shagnasty]

Are you supposed to be using "Reply All?"

First thing, if this "project" is sending with 150-200 email addresses in
the TO: field, tell them to figure out a way to manage their project
without exposing everyone's address to spammers and harvesters.

Tell them to read this: http://bccplease.com/

--
-bts
-This space for rent, but the price is high

[Restorm]

On 9/4/2012 10:46 AM, Jay Garcia wrote:
> On 04.09.2012 09:27, Restorm wrote:
>
> --- Original Message ---
>
>> I'm involved in some big global projects, where I sometimes have to
>> respond to emails that have 150-200 recipients. When I reply to them, I
>> get an error message saying that there are too many recipients. My ISP
>> says their limit is set at 200, so they are wondering if the limit is in
>> my email client. Anyone know if Thunderbird has such a limit?
>
> Not that I am aware of. Try sending in two batches.
>

That's not easy to do when I'm replying to an email, as I described above...

[Restorm]

On 9/4/2012 3:53 PM, Ron K. wrote:
> Jay Garcia on 9/4/2012 10:46 AM, keyboarded a reply:
>> On 04.09.2012 09:27, Restorm wrote:
>>
>> --- Original Message ---
>>
>>> I'm involved in some big global projects, where I sometimes have to
>>> respond to emails that have 150-200 recipients. When I reply to them, I
>>> get an error message saying that there are too many recipients. My ISP
>>> says their limit is set at 200, so they are wondering if the limit is in
>>> my email client. Anyone know if Thunderbird has such a limit?
>>
>> Not that I am aware of. Try sending in two batches.
>>
>
> Authenticate all the recipient addresses, that they are all valid. We
> have seen similar user issues here over the years where a single bad
> address causes the entire batch send to abort. Breaking the list down to
> smaller batches may aid finding the one causing a problem.
>

They're all good: it's the quantity, not the quality that's causing the
problem. And breaking it into smaller batches is hard when I'm replying
to an email.

[Restorm]

Thanks, Jay. Glad someone actually reads.

[Gelomida]

I wonder how bcc should help if a 'reply to all' should be possible.


Agreed: A mailing list seems to be more apropriate, but it's a pity to
artificially limit the number of recipients and making it impossible to
reply to all for mails, that were created with another email client.

What is also a pity is, that TB's error message just says, that there
are too many recipients, but that it does NOT say how many recipients
were allowed. This is very user unfriendly and should be rather simple
to be fixed.

[Beauregard T. Shagnasty]

Gelomida wrote:

> Beauregard T. Shagnasty wrote:
>> Restorm wrote:
>>> I'm involved in some big global projects, where I sometimes have to
>>> respond to emails that have 150-200 recipients. When I reply to them,
>>> I get an error message saying that there are too many recipients. My
>>> ISP says their limit is set at 200, so they are wondering if the limit
>>> is in my email client. Anyone know if Thunderbird has such a limit?
>>
>> Are you supposed to be using "Reply All?"
>>
>> First thing, if this "project" is sending with 150-200 email addresses
>> in the TO: field, tell them to figure out a way to manage their project
>> without exposing everyone's address to spammers and harvesters.
>>
>> Tell them to read this: http://bccplease.com/
>>
> I wonder how bcc should help if a 'reply to all' should be possible.

If a 'reply to all' is required, then that company needs to rethink their
strategies.

> Agreed: A mailing list seems to be more apropriate, but it's a pity to
> artificially limit the number of recipients and making it impossible to
> reply to all for mails, that were created with another email client.
>
> What is also a pity is, that TB's error message just says, that there
> are too many recipients, but that it does NOT say how many recipients
> were allowed. This is very user unfriendly and should be rather simple
> to be fixed.

I agree any error message should be more specific, but I have never run
into an actual limit. (Granted I don't send to 200 TO: people - the most
I've ever sent to were some club emails at around 140-150. I've since
changed my methodology for that, though.

I'm thinking the problem is more with the ISP limits than with our mail
client. A former ISP of mine (AT&T) would sideline outgoing mail that had
more than 25 TO: addresses to have someone manually check if it was spam.

Restorm says he sends to 150-200 and his ISP limit is 200. What is the
possibility that the one that bounced had 201 recipients?

[Mike Easter]

Restorm wrote:
> I'm involved in some big global projects, where I sometimes have to
> respond to emails that have 150-200 recipients.

That reminds me of a cartoon I saw today.

http://main.makeuseoflimited.netdna-cdn.com/wp-content/uploads/2012/08/email-management09.jpg?3e3c76


or http://bit.ly/Q2SY5B

Something is wrong with a communication process that exposes hundreds of
addressees to each other and then requires those hundreds to all be
using clients and providers which allow them to email hundreds of
recipients in a single mail with hundreds of To:/s.

A mailing list should be managed differently than that.

The addressees' email addresses should not be exposed to each other.
The/Your reply to the group/list should be addressed to the
majordomo/listserv not the hundreds of addressees.

--
Mike Easter

[Mike Easter]

Mike Easter wrote:
> Restorm wrote:
>> I'm involved in some big global projects, where I sometimes have to
>> respond to emails that have 150-200 recipients.

> A mailing list should be managed differently than that.
>
> The addressees' email addresses should not be exposed to each other.
> The/Your reply to the group/list should be addressed to the
> majordomo/listserv not the hundreds of addressees.

Also, a properly managed mailing list should allow for each and every
addressee's email address to not be exposed to any of those hundreds of
others who might be choosing for their own purposes to 'create' a new
mailing list, but also each addressee should be able to remove their
email address from the one and only mailing list in question by
contacting the listserv of this mailing list to which we refer.

Else it is possible that Restorm the OP or some other recipient of this
bulk emailing could be emailing some missive 'inappropriately' to all of
those hundreds of others.

What you are describing is a big mess which is clearly a mismanaged
mailing list. Those who improperly mail to such mismanaged lists
including Restorm replying are contributing to the spam problem and can
and should be listed on antispam blocklists.


--
Mike Easter

[Chris Ramsden]

> I'm thinking the problem is more with the ISP limits than with our
> mail client. A former ISP of mine (AT&T) would sideline outgoing mail
> that had more than 25 TO: addresses to have someone manually check if
> it was spam.
>

Ahem.

I quote myself, earlier in this thread.

"This site:

http://kb.mozillazine.org/Limits_%28Thunderbird%29

...says:

"E-mail addresses

There appears to be a limit of approximately 60 addresses when sending
messages if you enter each address separately. However, if you use lists
(mail distribution lists) for most of the addresses any limit is imposed
by whatever SMTP server you use."

There is a limit. It is published in a statement on a well respected
website. Why are we even discussing it?

[Mike Easter]

Chris Ramsden wrote:
> <BTS cite>

We are (still) discussing 'it' because

- 'it' - the initial post and the subthreads which then developed
vary; there isn't just a single 'it' any more
- the link you are talking about is addressing (something else;) the
difference between an initiating email creating a bunch of recipients by
individually populating a field such as To/CC/BCC by clicking addressees
one at a time vs populating such an initiating field by clicking a
group/mailinglist instead. Neither is happening in this thread; instead
the To or CC field/s is/are being populated 'automatically' in the reply
mechanism. Is that like individually or is that like group/list?
- the original premise is 'faulty' in that large mailing lists
shouldn't be handled the same way as a tiny little social 'group' in
which everyone knows everyone else and their address and approximate age
and weight and siblings and offspring, so 'we' can reply to several
friends and relatives all in the To: instead of a managed mailing list
and listserv addressed to the majordomo list manager.


--
Mike Easter

[Mike Easter]

Restorm wrote:
> I'm involved in some big global projects, where I sometimes have to
> respond to emails that have 150-200 recipients.

You don't have verifiable permission to email to those recipients.

http://www.spamhaus.org/whitepapers/mailinglists/ Mailing Lists -vs-
Spam Lists - The difference between senders of legitimate bulk email and
spammers couldn't be clearer, the legitimate bulk email sender has
verifiable permission from the recipients before sending, the spammer
does not.


Hopefully each of those recipients gave someone else - some other entity
- permission to email them - which permission that entity handled badly
- ie a mismanaged (or even 'mis-created) mailing list.

None of those recipients specifically, verifiably, and revocably gave
*you* such permission to email them (your reply/remarks/message), and/so
you should not *also* be handling/managing a 'mailing list' which you
acquired (in the To/CC) in 'not-a-proper-way' badly.


--
Mike Easter

[Restorm]

Well, I know that's not accurate. I regularly send to groups of 80-95
people...

[Restorm]

I don't have any control how they do things, nor am I in a situation to
make recommendations. It's not my project: I'm just involved. Any many
of these are overseas, often in developing countries.

[Restorm]

You're definitely right about that. If it knows it's over-lomit, then it
must know what that limit is, so why not just tell us? They do love to
keep their little secrets...

[Restorm]

No: there were 180 recipients, so that wasn't the cause. My ISP tells me
that even though their limit is 200, I might be getting limited by
Verizon. I was told that, if I used Port 587 and my ISP as the outgoing
server, I wouldn't be subject to Verizon's intrusions, but I guess
that's not true.

[Restorm]

Jeez, guys: READ, would you? I'm REPLYING to these emails, not sending
them (I'm getting heated because this is the third time this point has
been made).

[Beauregard T. Shagnasty]

Please explain the difference and the relationship between "my ISP" and
"Verizon." If Verizon is not your ISP, who is?

[Mike Easter]

Restorm wrote:

> Mike Easter wrote:

>> What you are describing is a big mess which is clearly a mismanaged
>> mailing list. Those who improperly mail to such mismanaged lists
>> including Restorm replying are contributing to the spam problem and can
>> and should be listed on antispam blocklists.

> Jeez, guys: READ, would you? I'm REPLYING to these emails, not sending
> them (I'm getting heated because this is the third time this point has
> been made).

When you create a (reply) message to a hundred (or more) people by
hitting reply, you are mailing to that 'list' of people/addresses and
not one single one of the list of addresses gave you a specific 'token'
or notification that they wanted to receive any mail from you.

Said another way, someone else has an improperly managed and likely
improperly created mailing list and they send you (a copy of) the list
in the form of the To: addresses.

Then, you take that improperly created and improperly managed list and
you 'copy' it by hitting Reply All and so you generate a new (reply)
mail addressed to all of those addressees.

Your use of Reply All does not relieve you of the responsibility of your
own mailing list mismanagement - abusive email practices. Just because
someone else is doing the wrong thing doesn't give you a license/right
to do it as well.

Perhaps if we were actually talking about the real thing (in terms of
the message) instead of a hypothetical email problem (too many
recipients) we could all clearly see the issue as a form of email abuse
just like spam, direct marketing, or targeted bulk email advertising or
other proselytization, political, religious or commercial.


--
Mike Easter

[Ron K.]

Restorm on 9/7/2012 6:37 PM, keyboarded a reply:

A TB capability is use of a Reply To: header in preference to use of the
To: header when replying to a mail item. The To: is the fallback method
of addressing replies.

[robertmiles]

Should be easy to fix if the email protocol allows a way for TB to ask
the email server how many recipients are allowed. Otherwise, don't
expect it to be easy.

You could ask that email server to add information on how many recipients
are allowed to their website describing how to set up email programs.

[Ron Hunter]

Years ago, someone asked about this issue, and I believe the problem was
that TB, or the ISP had a limit, not to the number of addresses, but the
length of the total field of addresses. So if you sent email to someone
with a short name, you could send to more people. Anyone else remember
this?

[Ron K.]

Ron Hunter on 9/8/2012 6:46 AM, keyboarded a reply:

>>>> Restorm wrote:
>>>
>>>>
>>>
>>>>> I'm involved in some big global projects, where I sometimes have to
> >>>> respond to emails that have 150-200 recipients. When I reply to
>>>>> them, I get an error message saying that there are too many recipients.
>>>>> My ISP says their limit is set at 200, so they are wondering if the
>>>>> limit is in my email client. Anyone know if Thunderbird has such a limit?
>>>

> Years ago, someone asked about this issue, and I believe the problem was
> that TB, or the ISP had a limit, not to the number of addresses, but the
> length of the total field of addresses. So if you sent email to someone
> with a short name, you could send to more people. Anyone else remember
> this?
>

Since I have no memory of such an old thread I have posted to
Moz.dev.apps.thunderbird asking for information whether TB has a TO:
header size limit.

[Ron Hunter]

On 9/8/2012 6:11 AM, Ron K. wrote:
> Ron Hunter on 9/8/2012 6:46 AM, keyboarded a reply:
>>>>> Restorm wrote:
>>>>
>>>>>
>>>>
>>>>>> I'm involved in some big global projects, where I sometimes have to
>> >>>> respond to emails that have 150-200 recipients. When I reply to
>>>>>> them, I get an error message saying that there are too many
>>>>>> recipients.
>>>>>> My ISP says their limit is set at 200, so they are wondering if the
>>>>>> limit is in my email client. Anyone know if Thunderbird has such a
>>>>>> limit?
>>>>
>
>
>> Years ago, someone asked about this issue, and I believe the problem was
>> that TB, or the ISP had a limit, not to the number of addresses, but the
>> length of the total field of addresses. So if you sent email to someone
>> with a short name, you could send to more people. Anyone else remember
>> this?
>>
>
> Since I have no memory of such an old thread I have posted to
> Moz.dev.apps.thunderbird asking for information whether TB has a TO:
> header size limit.
>

Even it TB doesn't, the mail server may. Multiple dependencies are
often hard to trouble shoot. Since he got the message, it seems to me
he should be able to reply to it....

[brian]

I'd want to know a bit more about Restorm's circumstances before I
called him a spammer (or pointed him to something defining him as one).

I've once been in his sort of situation, when I was instructed by the
person responsible for signing off my timesheets that I had to copy a
long list of people when answering e-mails to the project inbox. I'd
never heard of the vast majority of the CCs, let alone did I
personally have their permissions to send to them. I don't recall the
recipient list exceeding 25, though.

For some strange reason, I put earning my living at a higher priority
than worrying about what Spamhaus might think, and did as I was told.
I'm quite sure I would have been shown the door had I objected.


Brian.

[Restorm]

Sorry: trying to do too many things at one time, and a brain fart
slipped by. I meant to say web/email host, since my email is based on my
company's website.

[Restorm]

As I said: these are not technologically sophisticated users. But they
are most definitely NOT spammers. I agree that they should be using some
other technology for managing this dialog. They are working on
critically important projects to revitalize communities and restore
natural resources in lesser-developed countries. They have a lot of
people trying to help them, thus the number of recipients in their emails.

[Restorm]

Sorry, Ron: I'm missing your point. How does that change anything? Are
you saying that emails with a single "To:" and many "Bcc's:" are flagged
as spam more than those with just a "Reply To:" and a bunch of "Bcc's"?

[Restorm]

Thanks, Brian. If the poster had actually read the previous threads,
he'd know that I'm REPLYING to these emails, so there's no question of
my being a spammer. But the senders aren't either. As I said in another
thread just now (but will repeat here): these are not technologically

[Mike Easter]

Restorm wrote:

> They are working on critically important projects to revitalize
> communities and restore natural resources in lesser-developed countries.
> They have a lot of people trying to help them, thus the number of
> recipients in their emails.

Someone (some entity) should be put in charge of handling the mailing
list and that someone should be doing it properly.

There should be a 'process' or mechanism by which a person/address can
be added to the list and likewise a process by which a person can be
removed from the list.

When the mail goes out, it should be going out to all of the people who
want it, but their address should not be in the To/CC; and likewise when
you reply to the list, your reply should be going to the
listserv/majordomo not all of those To/CC addresses.

Another way to handle mailing lists is googlegroups or yahoogroups.
Such mechanisms also provide an alternate way to read the messages.



--
Mike Easter

[WaltS]

I don't know how many people are subscribed, but I just signed up for
the tb-planning mailing list.

I received my first message, and I'm sure others on the list also
received the message.

The message is To: "my email" From: tb-planning. My message header shows
a "Reply List" button. So I only have one address to reply to, but
everyone on the list will see my reply.

It sounds to me that whoever is sending you the email, does not know how
to create, and use a mailing list properly, and needs to be notified of
the problem with a request to create a proper mailing list.

--
Fedora 17 (64-bit)
Gnome or KDE Desktop
Thunderbird Beta
This space for lease

[Restorm]

I agree, Mike. But since (as I've explained several times earlier) I've
got no influence over the people managing these projects and sending
these emails, I'm looking for a solution to reality, to to an idealized
world.

[Restorm]

Thanks. I don't really understand how that works, but I'll forward your
idea to the people in charge of these projects.

[Ron Hunter]

A lot of people associated with clubs, and other organizations use email
to distribute club information, meetings, events, news, and often and
online newsletter. The local school systems all send email to all the
parents to keep them updated on things like school closings, etc. Of
course, they have their own servers, and domains, or at least the city
schools do, but that's not certain for rural systems.
Just because a person wants to send email to more than 100 people does
NOT mean they are spammers. It's not fair to assume that.

[Mike Easter]

Ron Hunter wrote:

> Just because a person wants to send email to more than 100 people does
> NOT mean they are spammers. It's not fair to assume that.

Proper email list management is not a black/white equation in which
there are only black spammers and white everything else.

There is all kinds of permission based direct marketing which is exactly
the same kind of content as spam based direct marketing and/but the only
difference is whether or not there is a proper structure for permission
based emailing.

Likewise social and political and religious emailings are not as simple
as such as black or white social 'spam' -- which social spam which is
pretty gray ends up with hundreds of people being emailed by a lot of
people who get the address from 'mismanaged' social mailing lists.

That very gray to black non-permission based social content bears no
resemblance to the permission-based commercial direct marketing -- so
permission based commercial bulk email direct marketing is *NOT* spam,
while non-permission based social 'bulkish' email *IS* what some would
term 'social spam' because spam is about permission vs not permission,
not on the basis of commericialization or profit or good deeds or good
intentions or any such thing.

Junk snail mail is bad, Junk faxes or junx is bad. Unsolicited/
Non-permission bulk email is bad.

Because the non-permission bulk email is such a problem, mechanisms for
remedying it at the client exist, and mechanisms for remedying it at the
server exist, and those mechanisms call it 'spam' regardless of whether
the content is wholesome or not.



--
Mike Easter

[Ron Hunter]

ANY email you don't want to see is SPAM, by MY definition. Since I
solicit very little email, and don't want any direct marketing messages
other than the ones I specifically sign up to receive, anything other
than those messages, and private messages specifically addressed to me,
is SPAM. On the other hand, I would MUCH rather the ISP NOT filter my
mail. I can manage that.

[Mike Easter]

Ron Hunter wrote:

> ANY email you don't want to see is SPAM, by MY definition.

Then we agree philosophically.

> Since I solicit very little email, and don't want any direct
> marketing messages other than the ones I specifically sign up to
> receive, anything other than those messages, and private messages
> specifically addressed to me, is SPAM. On the other hand, I would
> MUCH rather the ISP NOT filter my mail. I can manage that.

The worst kind of ISP (or personal) spam management is when mail is
'dropped on the floor' or lost sight unseen by the provider or recipient
in an effort to 'filter' or hide spam.

There should be zero loss of good mail. The strategies by which the
user filters mail or chooses a mail provider or chooses a mail provider
spam/filter configuration is up to how the recipient chooses to balance
inconveniences of possibly seeing presumably unwanted or questionable
mail vs the imperative of never losing a mail of quality unknown until
it is properly examined.


--
Mike Easter

[Ron Hunter]

There is the possibility that a user wants to receive porn ads, or
Nigerian financial scam email, for whatever reason.

[John H Meyers]

On 9/6/2012 11:39 AM, Chris Ramsden wrote:

> I quote myself, earlier in this thread.
>
> "This site:
>
> http://kb.mozillazine.org/Limits_%28Thunderbird%29
>
> ...says:
>
> "E-mail addresses
>
> There appears to be a limit of approximately 60 addresses when
> sending messages if you enter each address separately"

If true, it's a pathetically low limit, because many a message
can arrive from more liberal ISPs with between 100 and 500 recipients,
and all of those can appear in one incoming "To:" header
(such headers are typically multi-line, however,
containing multiple addresses per line).

Now, all you have to do is "reply all,"
and you'll then have a list of exactly that same size,
which would overwhelm any measly 60-address capacity
of TB, should that really be as many as it can handle.

If you save your message being composed as a draft
and then "view source," you will see that all the addresses
are in fact combined into one saved "To:" header,
while if you resume editing, TB now splits it up again
into its "one address per line with a button" arrangement
at the top, which might be the misfortune that could
set such a low ceiling on the size of even a "reply all" list.

Even as I check this out before posting, I see another TB bug
staring me in the face -- even if I carefully delete my
"Always BCC" addresses before I save a draft,
merely opening the saved draft to resume editing
re-inserts all my "Always BCC" addresses all over again,
despite that I already removed them during previous editing.

Returning back to composing a "To:" address list,
is it not possible to copy a large "To:" list
from any other message viewed in true "source" form,
with comma-separated addresses, and paste that into
any TB address line? IIRC, TB again immediately splits that
into the "one address per line with a button" format
that persists while you are actively composing,
and if that has a limit of merely 60 addresses in total,
it's vastly too small a limit to even match what's accepted
by many ISPs, in which case just doing "reply all"
to an incoming message from a high-limit source
would overwhelm poor underpowered TB.


As to someone's remark that a single "bad address"
could completely stop the mailing of a message having
many recipients, this does happen if the account's
outgoing server finds fault at once with any address,
while TB is still connected during the initial sending.

Improper syntax of even one address, for example, will always
"kill" an outgoing "send" attempt, as will the detection
of a non-existent local addressee *if* the outgoing server
checks that situation even while receiving recipient addresses
during the interactive connection between TB and that server
upon your pressing "Send." Once a list of recipients which
your outgoing "message submission" server can not check
for other than syntax has been initially accepted, however,
any problems detected only as that server forwards mail
to destination domains will simply be reported via email,
as "non-delivery reports" mailed back to the address in the
original "From:" header, and will have no impact
upon delivery to any other original addressees.

As to ISP limits, there can be combinations of per-message limits
with per-hour or per-day limits at more sophisticated ISPs,
in which case breaking up mailings might help overcome
any underpowered TB per-message limit,
but like your bank, which keeps debiting every separate charge
against your running account balance, you can still be "throttled"
by ISPs that count your overall sending over periods of time,
thus catching even those who use more professional mailing systems
that send a separate message for every single recipient.

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