SMTP Port Blocking Policy – Outgoing Mail Ports

Overview

To protect our network and customers from spam, abuse, compromised servers, and unauthorized bulk email activity, outgoing SMTP traffic is restricted by default on selected mail-related ports.

This is a security measure applied to customer servers and VPS instances.

Ports Blocked by Default

The following outgoing ports are blocked by default:

These restrictions apply specifically to outgoing connections from the customer's server/network.

Are Other Ports Blocked?

No.

Except for outbound SMTP ports 25, 465, and 587, we do not block customer ports as part of this SMTP restriction.

Other TCP/UDP ports remain available unless a separate security, abuse, network, or service-specific restriction applies.

Why Are SMTP Ports Blocked?

SMTP ports are commonly abused by compromised servers, malware, spam scripts, and vulnerable applications to send unauthorized email.

Blocking these ports by default helps:

• Reduce spam and email abuse

• Protect our network reputation

• Prevent compromised servers from being used for mass email

• Reduce the risk of IP addresses being blacklisted

• Protect other customers and upstream networks

• Detect and control suspicious outbound email activity

I Need SMTP Access. What Should I Do?

If your application or server requires outbound SMTP access through port 25, 465, or 587, you can submit a request to have the required port enabled for your IP address.

Your request should include:

• Server IP address

• Required SMTP port

• Purpose of the SMTP connection

• Email service/provider you intend to use

• Expected email volume, if applicable

• Any other relevant technical information

Our technical team may review the request before enabling SMTP access.

Important: Request Only the Required Port

Please specify the exact port you need.

For example:

"Please enable outbound TCP port 587 for IP x.x.x.x because this server uses an external SMTP provider for application email."

There is normally no reason to request all three ports if your application only requires one.

SMTP Port Selection

As a general guideline:

• Port 25 – Traditionally used for server-to-server SMTP delivery. It is commonly restricted because of abuse and spam.

• Port 465 – Commonly used for SMTP over SSL/TLS.

• Port 587 – Commonly used for authenticated SMTP submission and is generally preferred by applications and mail clients.

If your email provider supports 587, we generally recommend using it with authenticated SMTP submission.

Does This Affect Incoming Connections?

This policy concerns outgoing SMTP connections.

It does not mean that all incoming connections to these ports are blocked.

Incoming traffic is governed separately by your server firewall, security policy, network configuration, and the services running on your server.

Does This Affect Web, DNS, Database, or Other Services?

No.

The SMTP restriction only applies to the specified outbound SMTP ports:

25, 465, and 587.

It does not constitute a general port restriction on your server.

Security & Abuse Policy

SMTP access may be restricted, suspended, or reviewed if it is associated with:

• Spam

• Malware

• Phishing

• Unauthorized bulk email

• Compromised applications or servers

• Abuse complaints

• Suspicious outbound traffic

• Activities that negatively affect network or IP reputation

Customers are responsible for securing their servers and applications after SMTP access is enabled.

Frequently Asked Questions

Which ports are blocked?

Only outbound 25, 465, and 587 are blocked by default under this policy.

Are all ports blocked?

No. Other ports are not blocked as part of this SMTP restriction.

Can I request SMTP access?

Yes. Customers can request outbound access to the required SMTP port for their server IP.

Can I request port 25?

Yes, subject to review and approval.

Which port should I use for application email?

Where supported by your email provider, port 587 with authenticated SMTP submission is generally recommended.

Do I need to request all three SMTP ports?

No. Request only the port required by your application or mail provider.

What if my application cannot send email?

First verify which SMTP port your application is configured to use. If it uses 25, 465, or 587, you may need to request outbound SMTP access for your server IP.

Summary

Default outbound port policy:

• TCP 25 — Blocked

• TCP 465 — Blocked

• TCP 587 — Blocked

• ✅ Other ports — Not blocked under this policy

If your server requires SMTP connectivity, please contact our support/technical team with your server IP, required port, and intended use so that the request can be reviewed.