Hello every body,


I have configured two email server in postfix
A- is main email server with high priority
B- is the backup email server for the same domain with low priority.

Most of the time domain email is handeled by server A.

now when server A is down email will be recieved by by the backup email server that is B.

now when main server A comes back online again.

What will be about the Mails which have been recieved by the serer B (which was the backup email server)
How users will will recieve those mails now.

Plz reply me..


One the thing about this

I read in the book of postfix that if mail server is down the backup sever recieve the mail and when main email server (that has higher priority) comes back online then backup email server forward all email to mail email server.
Any body have idea how this can work.
what will be configuration for that.

If I understand your post correctly, then your primary mail server is also the final destination for all emails. i.e. The mailboxes reside on this server.

If this is the case, then your backup mail server should NOT be configured with your domain name listed in "mydestination" variable in main.cf. This tells postfix not to handoff the inbound e-mail to the local delivery agent (like procmail). Just put your domain name in relay_domains file and override the MX record used by the backup mail server by using the transport maps. This way, all e-mail is queued by the backup mail server and delivered when the primary becomes available.

Don't forget that spammers routinly go after the backup mail server because the primary "could" be configured to trust all e-mail from the backup mail server - thus bypassing spam checks, etc... Also, because the backup mail server does not have any local mailboxes, it will need to be configured to check for valid recipents while the primary e-mail server is down. This can be done with a local database (or LDAP) using the relay_recipient_maps option in main.cf.