I would like to disable reverse DNS lookups in Sendmail.
We have an SMTP relay, running Sendmail, with an IP-based access.db. We have no requirement for reverse lookups and, in fact, they may be contributing to delays in response time. This triggers alerts in monitoring ... which make people unhappy.
I've had a search and have been unable to find anything to disable reverse DNS lookups for incoming connections. Obviously I can't just kill all DNS lookups as no mail will then be delivered.
- OS: centos 5
- sendmail.x86_64 8.13.8-8.1.el5_7
- sendmail-cf.x86_64 8.13.8-8.1.el5_7
Thanks in advance!