I set up nginx as mail proxy, and it works for one domain, but won't work when I try to serve more that one domain each with different SSL certificate. Are there any way I can archive that, since nginx as mail proxy it quite good and seems to be good solution.

My fail is that I expected from mail servers the same I used to see in http server. Say, I tried to write this:

mail {
...
server {
listen 25;
protocol smtp;
server_name mail.domain1.com;
ssl_certificate mail.domain1.com.fullchain.pem;
ssl_certificate_key mail.domain1.com.key.pem;
starttls on;
proxy on;
xclient off;
}

server {
listen 25;
protocol smtp;
server_name mail.domain2.com;
ssl_certificate mail.domain2.com.fullchain.pem;
ssl_certificate_key mail.domain2.com.key.pem;
starttls on;
proxy on;
xclient off;
}
...
}

I expected nginx will choose right 'server' block based on server_name (which was wrong assumption) and then will use ssl certificate set in that server block.

I do understand I can set up LE certs with many hostnames included but say story is that domain list is too big to be included in single cert so I have to use more that one server block anyway.

Please advice!