To SEND email from your home computer, you need to make sure that your Mail program (Mail, Outlook, etc...) has the correct settings.
For an email address like firstname.lastname@example.org, your settings should look like this:
Mail Server Username: myname+mydomain.com ("email@example.com" will also work on some systems)
Incoming Mail Server: mail.mydomain.com
Outgoing Mail Server: smtp.mydomain.com (server requires authentication) port 26
You can ALSO use your home computer's ISP to send outgoing email on port 25.
For example: AT&T users would set their OUTGOING Mail Server to smtp.att.net on port 25.
Please submit a support ticket if you experience any issues with setting up your email.