The most common reasons for not being able to send emails through Outlook are wrong Outlook settings or blocked port 25 by the Internet Service provider.
To help you change your SMTP port in outlook, Click Here
Or;
Use the correct Mail Client settings:
- Incoming mail server (POP3/IMAP server): mail.yourdomain.com
- Outgoing mail server (SMTP server): mail.yourdomain.com
- Username: the full e-mail address like email@yourdomain.com
- SMTP authentication must be enabled for the login to be successful.
