How to work with Outgoing SMTP Port


If you are looking for what SMTP port you should choose for your SMTP server when you are sending important email to a client, this article is a must read for you.  Different SMTP port serves diversified purposes on time to time basis.

The Smtp port is the communication endpoints of a computer connected to a network. They are separated to differentiate the several processes and make it easier to handle, each one has a particular purpose and is associated to a specific protocol.


Smtp port 25 is the default port.  However, some IPs deny its use because of the massive spam and malware traffic by which is affected. This issue is raised in particular when you need to switch to another ISP – for instance when you’re traveling and connecting to a new service provider. In most cases, modern SMTP clients (Outlook, Mail, Thunderbird, etc) shouldn’t use this port.  Smtp port 25 is traditionally blocked, by residential ISPs and Cloud Hosting Providers, to curb the amount of spam that is relayed from compromised computers or servers. Unless you’re specifically managing a mail server, you should have no traffic traversing this port on your computer or server. The original/legacy email ports, 25 and 110, have been in use since the inception of email and have limited or no security features. As a result, port 25 has been used for the transmission of spam and malware from infected computers for nearly a decade. Port 110 simply is not a secure means of retrieving email. Port 995 provides SSL encryption when downloading email.

SMTP SSL Port and Port 587

Smtp SSL port stands for Secure Sockets Layer. It is a secure protocol for sending data safely and encrypted over the Internet. With SMTP SSL port encryption your user ID, password, and email are secured from hackers and identity thieves when sending or receiving email. In most cases, when there is an issue with the Outgoing SMTP with an ISP, the user will have followed all instructions for setup of their email application, and can properly receive email always. However, when sending out an email, they are able to either send out sporadically (such as “one email goes out every few hours but then second and third emails fail”) or not at all.

Port 587 is the port which almost all mail server supports. In fact, according to the relevant standard, this is the most preferred port for mail submission. But even if the mail server software supports it, it may or may not be turned on. You need to check with the administrator or hosting service. Not all large hosting services support port 587. SMTP by default uses TCP port 25. The protocol for mail submission is the same but uses it. SMTP connections secured by SSL, known as SMTPS, default to port 465 (nonstandard, but sometimes used for legacy reasons). This is the default mail submission port. When a mail client or server is submitting an email to be routed by a proper mail server, it should always use this port.

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