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Why Is SMTP Blocked??

Updated on 15 September, 2025

Outbound traffic on port 25 is blocked by default on new Vultr Compute Instances to prevent abuse and protect IP reputation.


By default, outbound traffic on port 25 is blocked on all new Vultr Compute Instances. This helps prevent abuse such as spam and protects the IP reputation of Vultr's infrastructure.

Why Port 25 Is Blocked

Port 25 is commonly used for unauthenticated or relay SMTP traffic, which is frequently exploited by spammers. To maintain a secure and trustworthy environment, Vultr blocks outbound traffic on this port by default.

Can I Send Email Using Other Ports?

Yes. You can still send email using ports 465 (SMTPS) and 587 (submission) through an external SMTP provider like:

  • Mailgun
  • SendGrid
  • Amazon SES
  • SMTP2GO
  • ElasticEmail

These providers support secure, authenticated mail delivery and are recommended over running your own mail server.

Requesting Port 25 Unblock

If you have a legitimate need to send mail over port 25 (e.g., legacy software that doesn’t support ports 465 or 587), you can submit a Support Ticket to request unblocking. Provide details about:

  • Your intended mail use case
  • Spam protection in place (SPF, DKIM, rate limits)
  • Expected sending volume

Approval is reviewed case-by-case and not guaranteed.

Note
Vultr recommends using authenticated mail relay services instead of hosting your own mail server. Running a self-hosted mail system requires ongoing monitoring, security hardening, and careful management of deliverability.