This guide is in reference to Mail Reflector and its MX record. Mail Reflector ensures you are able to receive email even if your ISP blocks port 25. It also provides all the features of Backup MX. Additions of a new MX Record to your mail server can take up to 5 minutes. It is advised to not try to send any mail until this time period has passed. Some mail servers might cache the old mail record, which will take additional time.
If sufficient time has passed and you are at the same location as the mail server, a www.portchecktool.com simple port check test on SMTP port 25 may also help diagnose the problem.