I investigated more: Location 1 (router behind CGNAT) As said yet I can't reach the target SMTP server, neither from router nor from the windows PC behind the router. I suspected a block imposed by...

@TimPitlinker From location 2: my suspect was right, I've tried to replace domain name of my email box with its IP address (same of SMPT server) and it worked. Let's suppose external SMTP server has...

@terziyski Already tried to replace smpt domain name with its IP address, and seem to pass the "wrong SMTP error" returned by router. Now it returns error about "wrong recipient". But that is...

@TimPitlinker Just tested from the router of the other location, it return an other error: Wrong email address. Please check the email address of the recipient. From a linux machine of this other LAN...

@terziyski The target SMTP server is listens on 25 port only. And it doesn't request any authentication, it works fine just without any encrypt SSL or similar. I tested it using very basic tools like...

I have a remote router TL-WR940N, and I'm trying to make it send its system Logs by email to a private smtp mail server listening on 25 port without authentication, so there isn't any SSL...