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Backup Mailserver -Secondary MX server
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John Hinton
Apr 1, 2013, 11:09:42 PM4/1/13
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My goal is to have a Postfix mailserver set up to accept mail for other
Postfix servers running multiple domains 'if and only if they are not
accessible'. I have been using Sendmail with milter-ahead set to:
"+backup-mx
For a backup MX or gateway, accept mail when the down stream mail
server is unreachable or when the server returns 421 server busy or 554
no service responses."
This provides a catchall system if and only if a primary server is not
accessible, thus eliminating the spam sent intentionally to the backup
system. Over the years this has worked great.
My searches are finding bad advice and not much in the way of this
particular need. (I remember having the same problem years ago when
trying to find something for Sendmail). It seems that the term backup is
a bit too broad a meaning for this purpose.
Anyway, if anyone has some good advice on what to use or where to start
reading, I would appreciate it.
And yes, sorry for the subject line yet again... It seems that secondary
MX server might be a better description?
--
John Hinton
877-777-1407 ext 502
http://www.ew3d.com
Comprehensive Online Solutions
Postfix servers running multiple domains 'if and only if they are not
accessible'. I have been using Sendmail with milter-ahead set to:
"+backup-mx
For a backup MX or gateway, accept mail when the down stream mail
server is unreachable or when the server returns 421 server busy or 554
no service responses."
This provides a catchall system if and only if a primary server is not
accessible, thus eliminating the spam sent intentionally to the backup
system. Over the years this has worked great.
My searches are finding bad advice and not much in the way of this
particular need. (I remember having the same problem years ago when
trying to find something for Sendmail). It seems that the term backup is
a bit too broad a meaning for this purpose.
Anyway, if anyone has some good advice on what to use or where to start
reading, I would appreciate it.
And yes, sorry for the subject line yet again... It seems that secondary
MX server might be a better description?
--
John Hinton
877-777-1407 ext 502
http://www.ew3d.com
Comprehensive Online Solutions
Wietse Venema
Apr 2, 2013, 8:15:53 AM4/2/13
to
John Hinton:
also networks. Network outages happen all the time in different
parts of the Internet.
As the result of outages in intermediate networks, the primary MX
server will be reachable for most clients but unreachable for others.
Therefore, the secondary MX server will see legitimate connections
while the primary MX server is up.
Secondary MX servers are a source of accept-then-bounce spam when
they don't reject mail with "recipient unknown", and when they don't
enforce the same anti-spam policy as the primary MXen. Such servers
may eventually become blacklisted.
Search the web for backscatter, outscatter, etc.
Wietse
> My goal is to have a Postfix mailserver set up to accept mail for other
> Postfix servers running multiple domains 'if and only if they are not
> accessible'.
What's missing from this picture that not only hosts can fail, but
> Postfix servers running multiple domains 'if and only if they are not
> accessible'.
also networks. Network outages happen all the time in different
parts of the Internet.
As the result of outages in intermediate networks, the primary MX
server will be reachable for most clients but unreachable for others.
Therefore, the secondary MX server will see legitimate connections
while the primary MX server is up.
Secondary MX servers are a source of accept-then-bounce spam when
they don't reject mail with "recipient unknown", and when they don't
enforce the same anti-spam policy as the primary MXen. Such servers
may eventually become blacklisted.
Search the web for backscatter, outscatter, etc.
Wietse
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