On Thursday 11 July 2002 06:52 pm, Sam Varshavchik wrote:
Yeah, so the secondary's going to try to immediately contact the primary,
which is temporarily unavailable (obviously), so the secondary is going to
defer the mail, and try again later. The mail that you see off the
secondary is from the secondary's redelivery attempt.
At my workplace, we have two domains setup where a secondary MX might be of
1. For one domain, a machine has two network interfaces, whose IP addresses
are the two MXes of that domain.
2. For the other domain, the two MXes (running sendmail) pass incoming emails
off to a third server where all mailboxes are hosted, to be retrieved by users
In both cases, the two MXes point to IPs hosted on different ISPs; and we do
have not very infrequent downtimes on either. ISPs in India aren't exactly
well known for their reliability ;-) As I see it, for domain 1, the second MX
helps only when a link goes down, but for domain 2, it helps even if one
of the MXes goes down too.