Is port 25 blocked by Plusnet?

[#1]

Just got FTTP a few days ago and have a static IP. I want (not need!) to run sendmail locally but whatever I do I cannot 'see' port 25 externally. So I wonder if there is some general block on port 25 (smtp) within Plusnet?

The port is forwarded correctly in the router and is open locally (other local systems can see it etc) but nmap from an external server does not see the port at all - it does see ports 80 and 443.

[#2 · Accepted solution]

Weird. I'm missing something obvious... sendmail burst into life and receives email fine. Maybe the MX record hadn't;t caught up since I changed the IP over (of course I forgot top check that nugget) and maybe the ISP I was trying the map from blocks port 25 this thwarting my nmap attempts. Anyway this is a non-issue.