CentOS 5.x / SendMail 8.14.x
I have a SendMail server that delivers all outbound mail to a downstream smarthost in the cloud:
define(`SMART_HOST',`relay:[example.blah.com]')dnl
example.blah.com has multiple A records and MTAs available to accept connections.
In the event that multiple emails need to go out at once, will sendmail establish multiple connections to the downstream smarthost? I did a few sanity checks and netstat suggests that sendmail will try using multiple simultaneous connections when things get busy.
If that's the case, what are the default rules governing that? How many connections will sendmail establish to a downstream source? When it's establishing these connections will it use the same A record that it resolved before? Or is it possible that these other connections could go to other A records/hosts?