The process of transferring emails from sender to recipient is performed via the Simple Mail Transfer Protocol (SMTP) . Email service providers have their own SMTP servers that are used to send emails to recipients’ servers. The sender simply creates an email, fills in their name and email address, and clicks “Send.” Email distribution is then managed by the SMTP servers maintained by the ESP.
However, in some cases, you need to provide the SMTP server details in the third-party tool. For example, in GlockApps, you have to create a sending account with SMTP settings to use the automatic email deliverability test. In this scenario, the SMTP server name, SMTP port number, username, and password are the required details. Sounds simple, doesn’t it?
Despite this, there SMTP Port: How to Choose are still
Misunderstandings about which SMTP port to choose, why, and what the actual differences between ports 25 , 465 , 587 , and 2525 are.
In this article, we’ll cover the basics of the most popular SMTP ports so that you can choose the correct port number when filling in your SMTP server’s details.
What is the SMTP port?
In the context of computers, a port is a logical address that identifies a specific network service. When a program wants to interact with a service running on another computer, it sends a message to a designated port on the target computer.
An SMTP port is a communication endpoint that handles. The transmission of democratic republic of the congo email list 243504 contact leads from one server to another. The SMTP port helps direct email traffic to the relevant mail server services that are responsible for message delivery and processing.
The SMTP port is defined by the Internet Assigned Numbers Authority (IANA) in consultation with the Internet Engineering Task Force (IETF). SMTP works on top of the TCP/IP protocol, which is the standard protocol for transmitting data over the Internet. TCP/IP allows SMTP to connect with other email systems and transfer electronic messages between them.
What are the most common SMTP port numbers?
The default SMTP port number is 25. In addition, SMTP often uses port numbers 465, 587, and 2525. Let’s review the different scenarios and examine when each port is used.
SMTP Port 25
Port 25 is the default SMTP port and has been used for decades to pass email between sending and receiving servers.
When sending an email, the email client connects to an outgoing mail server (SMTP server) through port 25, transferring important information such as. The email content and the recipient address. From there, the mail is managed by the SMTP server, protect your data and improve security which routes it to the recipient’s mail server using a variety of network protocols and technologies.
However, due to the increase in spam and email-based attacks, many ISPs and email service providers have begun blocking inbound connections on port 25. As a security measure, email service providers now use alternate SMTP ports to send emails, which provide a more secure means of data transmission.
SMTP Port SMTP Port: How to Choose 465
Email clients that want to transmit emails securely use SMTP port 465 as an alternative port number. Data security is ensured by SSL (Secure Sockets Layer) encryption on port 465.
When an email client connects to an SMTP server adb directory over port 465, email content, attachments, and authentication information are protected during transmission because of the SSL-encrypted connection between the client and server. By using encryption, you can keep conversations confidential and safe from prying eyes.
It is worth noting that the implementation of the TLS security protocol has made port 465 obsolete. However, many older email systems and SMTP clients still rely on SSL and continue to use port 465 as the default SMTP port number.
SMTP Port 587
Port 587 has been the standard port for SMTP SMTP Port: How to Choose message submission since 1998, with the approval of RFC 2476. Modern email clients connect to outgoing mail servers through port 587. While ISPs often restrict port 25 to reduce spam, SMTP port 587 is often open and can be used for encrypted email delivery.
SMTP port 587 is the recommended option for email transmission because it has the following advantages:
Enhanced security: TLS (Transport Layer Security) and STARTTLS (StartTLS) are two popular encryption methods that use port 587. Email content is protected while it is transmitted between systems over a TLS encrypted connection, ensuring a secure and impenetrable conversation.
Authentication: Users are typically required to authenticate with a username and password before sending email over port 587. This ensures that only authorized users can submit email for delivery and helps prevent unwanted access.
Privacy: While port 25
Is generally open to the public and can be used for other things besides email delivery. SMTP port 587 is used only for email transmission and is not intended for public use.
Delivery Optimization: Before accepting SMTP Port: How to Choose an email, a mail server can use port 587 to perform further checks, such as sender reputation analysis and spam filtering. This improves the overall deliverability of the message.
SMTP Port 2525
Port 2525 can be used when other SMTP ports are unavailable or unsupported. However, sending email using this port may not always be an option because not all. Email servers allow connections on this port and it is not officially recognized as an SMTP port by the IETF (Internet Engineering Task Force) or IANA.
What SMTP port to choose?
When you set up your email application to send emails, you need to use SMTP port 587 – this is the default and secure SMTP port for email transmission, which ensures secure data transmission via TLS.
If port 587 is blocked for some reason, you can try using port 465. Many providers still support this port for SMTP.
Port 2525 is a common alternative in situations where neither port 465 nor port 587 are available for SMTP connections. Although this port is not an officially recognized SMTP port, most providers allow it to be used for SMTP connections behind the scenes.
Finally, you should avoid using port 25 by any means, as most ISPs and hosting providers block inbound connections on port 25.
What happens if I use the wrong SMTP port?
If you enter an incorrect SMTP port number when configuring your email client, the email client will not be able to connect to the specified mail server through the defined port. The mail server returns an error message.
The following are the most common errors related to incorrect combinations of host and SMTP port numbers:
Unable to connect to SMTP server
Connection refused
Connection timeout
Nothing is listening on the remote host: port
Cause: The SMTP port is blocked by the firewall or the mail server does not support email delivery.
How to fix: Make sure nothing is blocking that port number; enter a different port number that is not blocked.
SMTP Authentication Failed
Username and/or password not accepted
Cause: The username and/or password for mail server authentication is incorrect or the mail server does not require authentication.
Unable to establish a secure connection
Cause: The wrong combination of SMTP port and security protocol or a problem with the SSL/TLS certificate.
Solution: Make sure the SSL/TLS certificate is valid; double-check the accuracy of the selected port number and security certificate.
Relay access denied
Unable to relay
Cause: The domain or IP address from which you are trying to send email is not allowed as a sending domain for the SMTP server.
How to fix: Make sure you entered the correct SMTP server name, port numbe. And security protocol; configure the SMTP relay settings on the SMTP server to allow your domain or IP address to send email.
It is important to remember that you can always contact your email service provider.ISP, or hosting provider to find out the SMTP server name, SMTP port number, and SSL. TLS protocol that you must enter when setting up your email client to send emails through their mail servers.
How to use SMTP port in GlockApps
GlockApps Email Testing Service allows automated email deliverability testing via sending accounts.
You enter the From email address and From name for sending mail to the seed email list. In addition, you need to enter the SMTP server name, SMTP port number, and security protocol. If the SMTP server requires user authentication, provide your username and password.
As mentioned above, you can get the exact SMTP information. Including the port number to use, from your email service provider or hosting provider.
It is worth noting that GlockApps supports two security protocols: none and SSL. The “none” protocol works the same way as STARTTLS. So if you enter port 587 which requires STARTTLS, select the “none” security protocol in the sending account settings.
GlockApps: Setting the SMTP port
A sending account with valid SMTP settings allows for quick testing of email by sending. Email to a proxy email address, and for running Inbox Insight tests on autopilot via automated testing.
