Unblock outbout TCP 25

Question

I want to unblock SMTP 25/TCP out. I'm using Plesk and I will need to send email outside the vm

Answer 1

Hi Starzone Services,

Good day, i hope you are doing great!

Welcome to Microsoft Q&A and thank you for posting your query here!

Outbound TCP port 25 (SMTP) is usually blocked by default on Azure for security (anti-spam) reasons, regardless of your local firewall settings in Plesk or the VM. If you need to send email directly from your VM on port 25, the unblock process depends on your hosting environment and subscription type.

Key Points for Plesk on Azure or Cloud VMs:

• Azure blocks outbound port 25 by default at the network level to prevent spam and abuse. This block applies whether you use Plesk, cPanel, or any other software. Adjusting local firewall rules in the VM typically does not resolve this issue.
• Enterprise-grade Azure subscriptions (EA or MCA) may be eligible to request unblocking of outbound port 25. For standard or pay-as-you-go subscriptions, this block usually cannot be lifted.
• To request an unblock (if your subscription is eligible), use the “Diagnose and Solve” section in the Azure Portal’s VM blade and locate the "Cannot send email (SMTP-Port 25)" diagnostic. Submit the unblock request as per Azure’s prompts
• If unblocking is not possible, use an SMTP relay. Configure Plesk to send mail via an external relay that supports authenticated connections, usually on ports 465 or 587, which are not blocked by Azure or most providers. Using SMTP relay is also considered a best practice for reliability and deliverability.

Steps You Should Follow:

1. Check your cloud subscription eligibility for port 25 unblock (consult Azure or your provider’s documentation). For more info: https://learn.microsoft.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity
2. If unblock is not possible or denied, set up Plesk to relay mail via a third-party SMTP provider (such as SendGrid, or your domain provider’s SMTP on ports 465/587). In Plesk, go to “Tools & Settings” > “Mail Server Settings” and configure outgoing mail relay details accordingly.​

If you’re on Azure pay-as-you-go or similar and need to send mail out, an SMTP relay is your best and most reliable solution

please do let me know if you have any questions on this!

If the provided information answers your query, do click "Upvote" and "Accept Answer", it will help others who might be facing similar challenges.

Thanks,

Harish.