CentOS 5.x / SendMail
Normally when I connect to my SendMail server, I see the SMTP banner greeting almost instantly.
I've noticed though, that when the primary DNS server is unavailable for the SendMail server to access, the SMTP banner greeting can take upwards of 10-15 seconds to appear. I assume that this probably has something to do with SendMail trying to perform a reverse DNS lookup, failing to receive a response, and then trying the second resolver (and/or giving up on the query).
Assuming this is the case, is this configurable? I reviewed the Tweaking Configuration guide (http://www.sendmail.org/m4/tweaking_config.html) and saw several options pertaining to resolver timeouts but they all seemed specific to OUTBOUND delivery FROM sendmail. This delay is happening for INBOUND delivery TO sendmail.
Any thoughts? Thanks.