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.
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 firstname.lastname@example.org
- SMTP authentication must be enabled for the login to be successful.
The most common mistake is to leave "My SMTP server requires authentication checkbox" unchecked. This option should always be enabled, since our servers require such authentication.
How to enable the SMTP authentication for Outlook:
From the File menu select the Account Settings button and then click on Account Settings. Select your email account under the E-mail tab. Click the Change button. Click the More Settings button at the bottom right. Select the Outgoing Mail Server tab and check the box My outgoing server (SMTP) requires authentication. Do NOT check the box next to Log on using Secure Password Authentication. Make sure the radio button is set to Use same settings as my incoming mail server. Click OK.
Check connection to port 25
The standard port usually used for SMTP connection is port 25. Most often the reason for failed email sending is that your Internet service provider blocks this port. If this is the case we recommend that you use the alternative port 2525 for your email SMTP connection.