VPS Port Restrictions - DigitalFyre Knowledge Base

Restricted Ports

Port(s)	Protocol	Direction	Reason
17	TCP/UDP	Both	QOTD — outdated protocol abused in amplification attacks
19	TCP/UDP	Both	Chargen — commonly used in UDP Reflection DDoS attacks
25	TCP	Outbound	SMTP — restricted to prevent outbound spam
26	TCP	Outbound	Alternate SMTP — blocked for the same reasons as port 25
137–139	TCP/UDP	Both	NetBIOS — associated with Windows file sharing and network enumeration
445	TCP/UDP	Both	SMB — commonly targeted by worms and exploits
465	TCP	Outbound	SMTPS — restricted due to potential misuse by automated spam tools
587	TCP	Outbound	SMTP submission — blocked to prevent unauthorized email transmission
1211	UDP	Both	Used by some P2P or legacy applications — restricted due to abuse potential
1688	TCP	Both	KMS — often abused in piracy-related traffic
1900	TCP/UDP	Both	SSDP — frequently abused in reflection/amplification DDoS attacks
53413	UDP	Both	Associated with UPnP-based attacks or malware

SMTP Port Unblocking

DigitalFyre will remove blocks on ports 465 and 587 upon request to support legitimate outbound mail via third-party providers such as Amazon SES, Mailgun, and SendGrid.

To request unblocking, open a support ticket and specify which ports you need opened and which mail provider you are using.

Port 25

Requests to open outbount port 25 are subject to strict review, and approval is not guaranteed. This port is heavily abused and is restricted to protect the network’s reputation.Accounts less than 6 months old are not eligible for submitting a request to enable port 25.

Requests to allow outbound port 25 will be rejected if they match common abuse patterns, including but not limited to:

Claims of sending “small newsletters” or transactional emails without a verified provider

Claims of running a “private email server” for personal use

Requests to “test an email script,” “test a mailer,” or run bulk mailing tools

Vague explanations such as “I need port 25 for my website.”

Self-hosted mail servers with no domain reputation, no SPF/DKIM/DMARC configuration, or no abuse handling policies

Any indication of bulk outbound emailing, purchased mailing lists, email marketing blasts, or mass outreach campaigns

Recommended Alternatives

For reliable outbound transactional email, use a dedicated third-party service like Amazon SES, Mailgun, SendGrid, or any verified transactional email provider — these work on ports 465/587 once unblocked.If you need managed email hosting rather than a self-hosted mail server, DigitalFyre offers Mailcow Email and Open-Xchange Email hosting services.