Just upgraded SME 6.01 to 7.4 and can't send email. I can't telnet to port 25 and can't receive mail from the outside. On 6.01, I used ssmtp/spop3 on ports 465/995, but sending that way doesn't work either, and I don't even see those options in server manager. I did a restore from 6.01 on a fresh 7.4 install.
When sending email from Horde, I get the error: "There was an error sending your message: unable to connect to smtp server localhost:25". I didn't intentionally do anything to block port 25.