Guide to SMTP Port Usage
Have you recently subscribed to SMTP server service but aren’t sure which port to use when sending emails? Read about notable SMTP ports in this article to determine which one is right for you.
Port 25
This is the default port that SMTP servers use, ever since 1982. Because the majority of emails are sent through this port, it’s very reliable. However, you’ll find that many IPs blacklist it because a lot of spam and malware is transmitted through it.
Because of that, you probably won’t want to choose SMTP port 25, as your messages may be denied.
MORE: SMTP Relay Office 365
Port 465
This SMTP port was used for SMTPS encryption and authentication so people could send emails safely over Secure Sockets Layer (SSL). However, port 465 was reassigned in 1998, which meant it had a deprecated SMTPS interface.
Because it’s now an outdated port, you’ll find that many SMTP relay service providers don’t support its usage. The ones that do only offer port 465 as an option to accommodate older Microsoft apps that don’t support STARTTLS.
MORE: Free SMTP Server List
Port 587
In late 1998, port 587 was set as the port to use for traditional message submission, while port 25 was designated for SMTP relay software.
Nowadays, most SMTP servers support the use of port 587. In fact, you should choose SMTP port 587 if you have an unencrypted or TLS connection.
MORE: Setup Gmail Outgoing Mail Server
Get some flexibility
If you use a managed SMTP service provider, you won’t have to worry about ports at all. Instead of being restricted to the use of one or two ports, you might get up to 7 ports or more for message relays.
With so many choices, you’ll be able to get around things such as ISP restrictions or a firewall blocking outbound SMTP. This can be extremely beneficial if you’re constantly sending out high volumes of emails. You’ll get reliable SMTP service with no hiccups in your email campaigns.
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