SMTP port which is also known as Simple Mail Transfer Protocol is the prime standard to send emails to the recipient's mail address through the internet. Apple Mail and Outlook are the applications that use SMTP to send emails to mail servers.

What is SMTP?

SMTP emails depend on the necessary domain names and relevant email addresses to send emails. All internet and mail users are conversant with the word-based form of various email addresses like Again email users understand that these text email addresses stand for a numeric IP address like


Well, many are unaware of the fact that these email addresses also include a specific "Port Number". An "SMTP port" denotes the explicit part of the Internet address which is purely used to send an email.

Difference between SSL and TLS

SSL or Secure Sockets Layer is a technology used to secure the internet connection. SSL secures sensitive data so that the data don't get hacked. Both SSL and SMTP facilitate the email sending option. As per experts, SMTP is the muscle and bones of the email process, and SSL is known as the skin so that emails can stay secure. SSL will always work with the obtainable port.


SSL was the necessary security protocol for all types of emails. Nowadays, TLS or Transport Layer Security is used in emails. This is an advanced technology that has made electronic communication more secure.

Both these protocols generate private channels that help in receiving and sending emails using the secure transmission. TLS helps in executing more hash functions to develop the encrypted communication and deliver more offers than its ancestors.


Many emails use many up-to-date conventions in the present time. SSL and TLS are combined via STARTTLS, which offers maximum security.

However, the SMTP protocol is not as secure on its own and uses the transfer method in conjunction. The conjunction method provides the utmost encryption protection. This is necessary for sending emails and enhancing SMTP transmission and SSL protocols.

How to find SMTP port?

You can get the hostname of the SMTP server and the necessary port number from the support page of your email service. Here you need to be contributed to the hosted email relay service.

Using PowerMTA

Users can easily find the information from the configured "SMTP-listener" directive within the config file of the PowerMTA. Many run their own SMTP server; if you too, you need to find the organised SMTP port number. Here you also need to get the address from the server configuration of the SMTP.

You can find that evidence from The config file, which is available in on a Linux server. It is also available in on Windows Server.

Which port should you use for SMTP?

Many ask which port they should use for SMTP? These are Ports 25, 465, 587, or 2525 for SMTP. These all are considered standard SMTP ports at some point.

Again, those configuring their systems to use SparkPost as an SMTP transmit need to use port 587 as the standard SMTP port. This should also be used along with 2525 as a substitute in case port 587 is unavailable.

MailSlurp mailserver ports

Here are the main URLs for IMAP and SMTP access using the MailSlurp mailservers as an example:

SMTPmx.mailslurp.com2525falseSMTP server
IMAPmailslurp.click1143falseIMAP server

Notice the lack of TLS. This is in order to support older clients.