We have 2 SMTP gateway running Solaris 10 to relay mails to external. The 2 SMTP servers smtp-1 and smtp-2 are installed in different data center and load balance by F5 load balancer.
When we shutdown the DC that installed with smtp-1 for maintenance and configured the load balance to route mails that going out to use smtp-2. We experienced that mails are not able to send out found the following in the log:
<date> smtp-2 sendmail: [ID 801593 mail.info] uBHGEiBr013709: to=<firstname.lastname@example.org>, delay=00:15:55, xdelay=00:15:55, mailer=esm
tp, pri=120318, relay=mailhost.com, dsn=5.3.5, stat=Local configuration error
When the DC is up, the SMTP mails are back to normal.
What could be the problem?