Using the code below, I can't connect to any MX servers that I find with nsloookup -type=MX. I don't think the ports are blocked though, since I can use Thunderbird with my Gmail account. Any suggestions?
posted 8 years ago
Gmail uses a secure SSL POP/SMTP connections that aren't blocked by ISP's. It may be that your ISP is only allowing you connections to it's own SMTP server and no others ... this is to prevent spam.
To verify try connecting manually to one of the MX hosts using telnet command:
telnet hostname 25
If you get a response your ok. Otherwise your ISP is blocking you.