Proxy smtp traffic?

Question

SMTP

Tell me how you can implement proxying of smtp traffic in special software, which does not have the ability to configure smtp proxy. What about the special The software is installed under windows server and, accordingly, each user should be able to choose a proxy server for smtp, from which he can now send a letter. VM deployed on proxmox hypervisor

Answer 1

There is no proxy for smtp.
Or more precisely, any smtp transit node is a proxy. You describe the problem in more detail. For now, you want the impossible.

Answer 2

SMTP proxy (smtpp) is in 3proxy, the destination server can be passed via username, but is not supported by SSL / STARTTLS, so it will only work if the destination servers do not require mandatory SSL for authentication, see
https://3proxy.ru /doc/man8/smtpp.8.html