SMTP Authentication Restriction Between Two cPanel Servers

Haziq haziq

• December 29, 2025 08:06

Hello Support,

I would like to seek clarification regarding an SMTP setup issue.

My website and email are hosted on two different cPanel servers with different IP addresses, but under the same domain.
When the website server attempts to send emails via SMTP using an email account hosted on the email server, the connection is successful but SMTP authentication fails, even though the credentials are correct.

I would like to ask:

• Is SMTP authentication from an external server blocked by default on your email server?

• If yes, is it possible to whitelist the website server IP to allow SMTP authentication?

• Are there any recommended settings (relay / smarthost) for this type of setup?

Thank you for your assistance.

Best regards,
Haziq Anuar

• 

  cPRex Jurassic Moderator

  • December 29, 2025 16:56

  Hey there!  I'm not aware of anything that would be blocking the SMTP authentication as what you're describing is a common setup both in cPanel and other platforms.  Could you share specifically what shows up in the mail log when the authentication fails?

   

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