(Rude side note: You are using an outgoing mail server that you don't
trust. This is a problem that you need to correct.)
No. I trust the mail server to only be used by authorized users. It's the
other users I don't trust.
From you previous posts, I understand that your ISP's MTA uses SMTP AUTH...
So, your ISP's MTA allows authenticated users to pretend to be anyone? On a
properly configured MTA, when you authenticate you are only allowed to send out
using particular e-mail addresses/domains assigned to your account.
Also, I know this might sound rude or uncaring, but if you are really worried
about being blacklisted because you use a shared MTA that is insecure, then
doesn't it seem reasonable that you would pay for access to a properly secured
MTA? I mean, there is no free lunch.
Michael R. Brumm