Not sure which SMTP port to use? The difference between SMTP port 25 vs 465 vs 587 is simple. Port 25 moves email between mail servers. Ports 465 and 587 let email apps send messages. However, they protect connections in different ways. Here is how to choose.
SMTP Port 25 vs 465 vs 587: Quick Comparison
| Port | Main purpose | Security | Best for |
|---|---|---|---|
| 25 | Server-to-server delivery | STARTTLS when available | Mail servers |
| 465 | Email submission | Implicit TLS | Email apps and websites |
| 587 | Email submission | STARTTLS, with TLS required | Email apps and websites |
What Is SMTP Port 25?
Port 25 carries messages from one mail server to another. For example, your VPS uses it to contact a recipient’s mail server. Therefore, you need this port for direct email delivery.
However, some VPS providers block outbound port 25 to reduce spam. Also, servers may offer STARTTLS, but they do not always require encryption.
If you run your own mail server, consider CybroHost SMTP VPS Hosting. Its Linux plans include port 25 access and PTR/rDNS control. Even so, you still need email authentication and a good reputation.
What Is SMTP Port 465?
Port 465 lets email clients submit outgoing messages. It starts an encrypted TLS connection immediately. This approach is called implicit TLS.
Use port 465 when your email provider recommends SSL/TLS. Then enter the SMTP hostname, username, and password it supplies.
For example, a mail app can use this port to send a message securely. Still, port 465 does not guarantee that the message reaches the inbox.
What Is SMTP Port 587?
Port 587 also handles outgoing email from apps. However, it starts with a normal SMTP connection. Next, the client uses STARTTLS to turn on encryption.
Your app must require TLS before it sends your password or message. So, never allow an unencrypted fallback.
Both ports can protect your email when configured correctly. The IETF email security standard (RFC 8314) explains how implicit TLS and STARTTLS work.
Which SMTP Port Should You Use?
- Running your own mail server? Use port 25 to deliver mail to other servers.
- Setting up Outlook or Thunderbird? Choose 587 with STARTTLS or 465 with SSL/TLS.
- Configuring WordPress SMTP? Follow your SMTP provider’s recommended submission port.
If sending fails, check the hostname and password first. Next, confirm the port and TLS setting. Finally, inspect your firewall and any provider restrictions.
Remember, an open port alone does not improve deliverability. SPF, DKIM, DMARC, and sender reputation still matter.
FAQs
Is SMTP port 465 safer than 587?
Not automatically. Both can encrypt your connection. The main difference is when TLS starts.
Can I send email without port 25?
Yes. Your app can use an external SMTP relay on 465 or 587. However, direct mail-server delivery normally needs port 25.
Which SMTP port should I use for WordPress?
Use the port your SMTP provider recommends. Usually, that means 587 with STARTTLS or 465 with SSL/TLS.
Final Recommendation
Use 25 for server-to-server delivery, 465 for immediate TLS, and 587 for STARTTLS submission. Match your provider’s settings. Then send a test email before going live.
