Port 25 Policy: Why Outbound SMTP Is Blocked
Outbound port 25 is blocked by default on VPS and VDS. Learn why, how to ask us to open it with a ticket and how to send email over port 587 or 465.
On SolumeCore VPS and VDS servers, outbound port 25 (SMTP, the port mail servers use to hand messages to each other) is blocked by default. Your server can send email without any problem over the authenticated submission ports 587 and 465, for example through an email sending service (SMTP relay). If you need to deliver email directly from your server over port 25, you can ask us to open it with a ticket.
Why it is blocked
Port 25 is the most abused path for sending spam. A single compromised or misconfigured server is enough to get an IP onto blocklists, and that also affects other customers on the same network. With the default block:
- An infected server cannot turn into a spam source without you noticing.
- Everyone's IPs keep a good reputation, so your emails are more likely to reach the inbox.
- Only servers that really need direct email, and are set up to do it properly, send it.
This is part of the network restrictions described in our Terms (section 15.6) and our acceptable use policy.
What is blocked and what is not
| Traffic | Status |
|---|---|
| Outbound to port 25 (direct email delivery) | Blocked by default |
| Outbound to port 587 (submission with STARTTLS) | Allowed |
| Outbound to port 465 (submission with TLS) | Allowed |
| Email from web hosting accounts | Not affected (see below) |
If you have web hosting with us, your email accounts send through the hosting's own mail server, over port 465. This policy does not affect them; see how to create an email account on your hosting.
The recommended alternative: an SMTP relay on 587 or 465
For most cases (contact forms, app notifications, WordPress emails, bot alerts) you do not need port 25. The simplest option, and the one with the best deliverability, is to send through an email sending service (also called an SMTP relay or transactional email) or through your email provider's SMTP server:
- Create an account with the sending service you prefer and verify your domain. It will ask you to add SPF, DKIM and, ideally, DMARC records to your domain's DNS; see how to edit DNS records.
- Write down the SMTP server, the port (587 with STARTTLS or 465 with TLS), the username and the password or key the service gives you.
- Configure your application or your mail server to send through that server. For example, in Postfix:
relayhost = [smtp.example.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- Check from your server that you can reach the submission port:
nc -vz smtp.example.com 587A message like succeeded or open means the port answers. If you test port 25 instead and it does not connect, that is the block working as expected.
If your application lets you choose, use port 587 with STARTTLS. If it only supports connections that are encrypted from the start, use 465.
How to ask us to open port 25
If you really need to deliver email directly from your server (for example, because you run your own mail server), open a ticket:
- Log in to dashboard.solumecore.com and go to Tickets › New ticket. The step-by-step guide is in how to open a support ticket.
- In Topic, choose the VPS or VDS you will send from.
- In the subject, write something like "Request to open port 25".
- In the description, tell us:
- What you need it for and which software you will use (for example, Postfix).
- The domain you will send from.
- That you have already set up SPF, DKIM and DMARC for that domain.
- Roughly how many emails you expect to send per day.
- That your recipients asked to receive your emails (no purchased lists).
We review every request by hand and reply in the same ticket. We may ask you for more information before deciding.
What we do not promise
- Not every request is approved. We decide based on the use you describe, the account's history and the type of service.
- Opening it can be reversed. If we detect spam, receive complaints or the IP lands on blocklists because of your sending, we block the port again, as the acceptable use policy explains.
- We do not guarantee delivery. Whether your emails reach the inbox depends on your setup, your domain's reputation and the providers that receive them.
- There is no fixed turnaround. We handle these requests like any other ticket, by priority.
FAQ
Why can't I send email from my VPS?
Your application is most likely trying to deliver email over port 25, which is blocked by default. Configure it to send through an email sending service over port 587 or 465.
Are ports 587 and 465 blocked too?
No. You can use them to send authenticated email through a sending service or your email provider's SMTP server.
How do I ask you to open port 25?
Open a ticket from the dashboard choosing your VPS or VDS, explain what you need it for and include the domain, the approximate volume and that you have already set up SPF, DKIM and DMARC.
Does this affect my web hosting email?
No. Web hosting email accounts send through the hosting's mail server over port 465.
Does opening the port in the panel firewall unblock it?
No. The panel firewall controls the traffic that reaches your server. Only our team lifts the outbound port 25 block, on request.