SMTP error: Invalid address

[robert.mag...@gmail.com]

I wrote a PHP5 program sending emails with PHPMailer. The problem is that when I try to send email from myn...@mydomain.com (I have such accound) I receive error:
SMTP error: Invalid address: myn...@mydomain.com.
My domain is registered. A few weeks ago everything was working fine.
Could you tell me please what are possible reasons of this error?
Thanks in advance.

[Eli the Bearded]

There's nothing here that hints as to what the problem is. Some things
that could be going on:

The mail system on the host that runs the PHP program
is borked. Can you send mail from it using a different
program? Even just a bare mail() from PHP would be a
starting sanity check.

The network the host that runs the PHP program is on is
borked. Again can you send mail using a different program?

There is something wrong with the destination; I checked
mydomain.com and it seems to have a valid SMTP listener,
but you probably lied about the email address.

There is something else wrong, such as unprintable
characters in the email address that you didn't cut and
paste.

Maybe it was even a transient error related to some
temporary condition.

Elijah
------
mydomain.com. 86400 IN MX 0 mx.mailix.net.

[Sam]

The only party who can give you an authoritative reason for this, or any
other, error is the administrator of the mail server that rejected a message
with the error. Any mail server is free to reject any email for any reason
it wants. Although, in most cases, the reason for the rejection can be
determined from the message, in cases where it's not, only the mail server
that rejected a particular SMTP transaction will know why it did so.

[Chris Davies]

Eli the Bearded <*@eli.users.panix.com> wrote:
> There is something wrong with the destination; I checked
> mydomain.com and it seems to have a valid SMTP listener,
> but you probably lied about the email address.

Valid listener, but no such address (also assuming that the address
given by the OP is actually correct):

$ host -t mx mydomain.com
mydomain.com mail is handled by 0 mx.mailix.net.

$ host mx.mailix.net
mx.mailix.net has address 66.11.225.84
Host mx.mailix.net not found: 3(NXDOMAIN)
Host mx.mailix.net not found: 3(NXDOMAIN)

$ nc -vvv 66.11.225.84 smtp
Connection to 66.11.225.84 25 port [tcp/smtp] succeeded!
220 mx.mailix.net ESMTP Exim 4.71 Wed, 12 Sep 2012 01:02:24 -0700
HELO boo
250 mx.mailix.net Hello boo [{your_ip_address}]
MAIL FROM:<>
250 OK
RCPT TO:<myn...@mydomain.com>
550 unrouteable address
QUIT
221 mx.mailix.net closing connection

Chris