Last updated: July 2026

In short: DigitalOcean blocks outbound SMTP traffic across ports 25, 465, and 587 on all Droplets and Reserved IP addresses by default. Because of severe IP reputation and maintenance overhead, DigitalOcean recommends against running self-hosted mail servers and advises routing mail through third-party email providers.

When launching a virtual server on DigitalOcean to host web applications or a dedicated email server, standard email delivery will fail immediately. Unlike most cloud providers that restrict only direct server-to-server delivery over port 25, DigitalOcean enforces a comprehensive network restriction across all standard mail transmission ports.

Total SMTP block across all Droplets and Reserved IPs

DigitalOcean blocks not only direct outbound SMTP connections on port 25, but also the standard submission ports used for authenticated relaying (465 and 587).

According to official DigitalOcean support documentation: SMTP ports 25, 465, and 587 are blocked on Droplets to prevent spam and other abuses on our platform. This block applies to all Droplets by default and includes traffic passing through a Reserved IP address.

Because this restriction is enforced at the data center network edge, assigning a static Reserved IP address or modifying local operating system firewalls (iptables or ufw) will not enable traffic on these three SMTP ports.

Why DigitalOcean recommends against self-hosting

The aggressive network restriction stems from the ongoing challenge of securing cloud subnets against automated abuse. DigitalOcean explicitly warns developers against self-hosting email infrastructure: Even if SMTP were available, we strongly recommend against running your own mail server , as self-hosted mail servers are difficult to secure and maintain, frequently get flagged as spam, and require constant monitoring to protect your IP address.

(Note: The space preceding the comma in the quote above appears verbatim in official DigitalOcean documentation.)

IP reputation reality check

DigitalOcean’s warning regarding IP monitoring reflects actual deliverability conditions across cloud hosting ranges. Because Droplet IP pools are dynamically recycled across thousands of developers and frequently targeted by bad actors, data center subnets carry significant pre-existing reputation issues.

Frequently, Droplet IP ranges are listed on strict blocklists (DNSBLs) such as UCEPROTECT (Level 2 or 3) and Spamhaus. Even if a server administrator attempts to deliver mail directly from a cloud instance, major receiving platforms (such as Gmail, Yahoo, and Outlook) routinely reject or quarantine messages originating from hosting subnets, despite valid SPF and DKIM signatures.

Because standard SMTP ports are blocked across Droplets, DigitalOcean guides users toward external delivery integrations: To send mail from services hosted on DigitalOcean, we recommend using a third-party email as a service provider.

To deliver transaction notifications or application mail from DigitalOcean Droplets, developers typically integrate with third-party email providers over HTTP APIs (using standard HTTPS port 443, which is unblocked) or via alternative custom relay ports supported by the provider.

If your external email provider supports authenticated SMTP relay over an alternative, non-blocked custom port, a typical Postfix configuration (/etc/postfix/main.cf) looks like this:

relayhost = [smtp.provider.com]:2525
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_security_level = encrypt

Or send reliably via Dispatch. If you want to avoid blocked SMTP ports, complex API integrations, IP deliverability monitoring, and self-hosted mail server maintenance, you can route your application mail quickly and securely via Dispatch.

Verifying your configuration

Once your third-party provider or relay path is configured, verify your email authentication records (SPF, DKIM, DMARC) and domain health using the free MXAudit scanner.

Further reading