The most common reasons for not being able to send emails through Outlook are the wrong Outlook settings or blocked port 25 by the Internet Service provider.
The following are some of the checks which you can make to assure that you do not face this problem.
Use the correct Mail Client settings-
- Incoming mail server (POP3/IMAP server): yourdomain.com
- Outgoing mail server (SMTP server): yourdomain.com
- Username: the full e-mail address like firstname.lastname@example.org
- SMTP authentication must be enabled for the login to be successful.
NOTE: Please do not use secure authentication to your mail server.
Check connection to port 25-
The mistake one makes is to leave My SMTP server requires Authentication checkbox unchecked. This option should always be enabled as most mail servers need such authentication. Port 25 is the standard port used for SMTP connection. Very often the main reason for failed email sending is that your internet service provider blocks this port. If this happens it is best that you use the alternative port 2525 for your email SMTP connection.