SMTP Restrictions and External SMTP providers

HappyFeat

• August 28, 2025 09:30

All of the mail sent from our server is sent using PHPMailer via SMTP2Go on port 2525.

If I enable SMTP Restrictions, will it prevent our mail from being sent?

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  cPRex Jurassic Moderator

  • August 28, 2025 14:08

  Hey hey!  Probably - does your form authenticate to any specific account on the server?

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  quietFinn

  • August 28, 2025 18:35

  cPanel SMTP Restrictions blocks port 25, 465 & 587, so if you send on port 2525 you should be fine.

  Then of course tcp port 2525 out must be open in the firewall.

   

   

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  cPRex Jurassic Moderator

  • August 28, 2025 19:43

  That's a good point - since the port is customized the SMTP Restrictions may not apply here at all!

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  Rubfy

  • August 29, 2025 18:11

  Yes—this works fine.

  We run with SMTP Restrictions enabled and relay mail from apps via an external provider. SMTP Restrictions only blocks user processes from using 25/465/587; using a custom port (e.g., 2525) continues to work.

  Checklist

  • Open outbound TCP 2525 in the server firewall.

  • In your app (PHPMailer), use AUTH + STARTTLS on 2525.

  • Add the provider’s SPF include, enable DKIM at the provider, and keep DMARC aligned.

  • Optional: if you ever must use 587, set a smarthost in WHM » Exim Configuration so mail goes out via Exim (still compatible with SMTP Restrictions).

  Minimal PHPMailer example

   

  $mail->isSMTP(); $mail->Host = 'smtp.your-relay.example'; // e.g. smtp2go.com or sendgrid.net $mail->Port = 2525; $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS; $mail->SMTPAuth = true; $mail->Username = 'your_smtp_username'; // some providers use "apikey" $mail->Password = 'your_smtp_password_or_api_key'; $mail->setFrom('no-reply@yourdomain.com', 'Your App');

  We use this pattern in production (with a relay provider) and haven’t had issues.
  If you want, I can share a quick SPF/DKIM template or a sample Exim smarthost config.

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  HappyFeat

  • August 31, 2025 23:09

  Thanks everyone I'll give it go and see what happens.

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