if I remember correctly, the last time I tried Postfix on OpenBSD, I can
use self-generated SSL cert. Hope it's helpful to you.
self-signed certs can work with mail smtp servers postfix or sendmail,
man starttls
But when you used self-signed certificates, other servers or clients
may at a minimum give warnings to users. also it is plausible that
using a certificate signed by a recognized CA may help when sending
to larger corporations or maybe not....
If you setup SMTP-AUTH, and have clients require TLS, the clients
will likely get a warning message till they accept and store it.
Thats okay for a a handfull, but for the non literate or commerce
customers it will be an education pain and then most admins
will donate $16 rather than have to explain to clients about accepting
certificates not signed by trusted CA.....
thats my $0.02 on justifying $16
;)
