This is odd....I've never thought of it before because I've never had to consider it. But, is there an accepted way to specify a default MTA that worker servers should use? i.e. suppose you have:

mailserver.domain.tld
server1.domain.tld
server2.domain.tld
server3.domain.tld

What should be done such that server[1|2|3] does not have to run either sendmail or postfix to get mail to mailserver? i.e. How can you tell the 3 worker servers to just open an smtp connection to mailserver for all outbound mail?

Maybe I haven't thought about this problem in the right way, but it's got me stumped at the moment haha.

Thanks,
Phil

To my knowledge, they need some sort of MTA running in order to send email.

There are very trivial MTAs that may suit your needs (ssmtp, mini_sendmail, smtpclient, etc.). Any of these will likely suit your needs, provided your client's do not require or call the sendmail binary (which is supplied with Sendmail, Postfix, Exim).