Short answer: yes. Only port 25 is disabled by default on DartNode services, and you can request access to it yourself from your dashboard. Ports 465 and 587 are open, so you can send through an SMTP relay or mail provider right away. This is the most common question we get, so this page explains how it works.

Which SMTP ports are open?

The port 25 default applies to outbound connections over both IPv4 and IPv6, on all service types. Inbound mail isn't affected, so your server can always receive email on port 25. Webmail, IMAP (143/993), and POP3 (110/995) also work normally.

In practice, you only need to request port 25 if your server delivers mail directly to recipients' mail servers (for example, running your own Postfix or Exim mail server without a relay). If you send through a relay or email provider on 465 or 587, you don't need to request anything.

How to request port 25 (SMTP) access

1. Log in to your dashboard at app.dartnode.com.
2. Open the main menu.
3. Select SMTP Request and submit your request.

You can also go straight to the request page: app.dartnode.com/network/smtp.

When SMTP gets disabled again

Once enabled, SMTP access is disabled automatically if abuse is reported against your service, or if abuse is detected by our network intelligence systems. Spam, compromised servers, and mail that gets your IP listed on blocklists will all trigger this.

We do this because outbound email is the most abused feature of any hosting network. One compromised server sending spam can get a whole IP range listed on Spamhaus and other blocklists, and then mail from every customer in that range gets rejected. Keeping port 25 off by default, and shutting it off quickly when abuse appears, keeps our IP space clean for everyone who sends legitimate mail.

Keep your server patched, use strong passwords on mail accounts, and don't run open relays. If your access is disabled, fix the cause first, then contact support.

Sending without port 25: use a relay or email API

An SMTP relay (also called a smarthost) or a transactional email API works without requesting port 25. Your server hands the message to the provider, which delivers it from its own well-reputed IPs. That often gives better inbox placement than sending from a fresh server IP anyway.

Relay on port 587 or 465

Point your mail server or application at your provider's host on port 587 (STARTTLS) or 465 (implicit TLS) with authentication. For example, in Postfix /etc/postfix/main.cf:

relayhost = [smtp.your-provider.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_security_level = encrypt

A full walkthrough is in How to Set Up an SMTP Relay.

Send over HTTPS with an email API

Most transactional email providers offer an HTTP API. Your application calls it over port 443. If you're sending from code (password resets, notifications, receipts), this is usually the simplest route.

Either way, set up your DNS

Publish SPF, DKIM and DMARC records for your domain. Without them, mail lands in spam no matter how it's sent. See DNS Records for Email Deliverability.

Common questions

I can't receive email either. Is that the port 25 default?
No. Inbound port 25 is always open. Check that your MX record points to the server, that your mail server listens on port 25, and that your own firewall (UFW, firewalld) allows it.

Will this affect my control panel's mail (cPanel, Plesk, HestiaCP, and so on)?
Only if the panel delivers mail directly over port 25. Either request SMTP access as described above, or set the panel's "smarthost" or "relay" option to use a relay provider on 587 or 465.

Do I need rDNS?
If you send mail directly from your server over port 25, a matching reverse DNS (PTR) record is strongly recommended, since many receiving servers check it. When you send through a relay, the relay's rDNS is the one recipients check.

Need help?

Open a ticket or email [email protected].