So, the IMAP protocol gets access to the email from any device or location if authorized. IMAP stores emails on a remote server and downloads them on demand when the recipient opens them. Today, its fourth version is in use, hence the name IMAP4. Internet Message Access Protocol (IMAP) is a communication standard for accessing emails. Both of these servers are message accessing agents (MAAs). Once the email knocks at the mail server’s door, either IMAP or POP3 will be used to retrieve it. IMAP4 and POP3 – protocols to receive emails So, if the use of the default SMTP port causes some trouble, try 2525.įor more on this, read our blog post about SMTP ports. 2525 is secured similarly to 587 and is often used in lieu of it. It is not an official SMTP port, but almost any email service provider supports it. TLS encryption ensures the secure submission of the email. Nevertheless, today many servers still use SMTPS and maintain 465.Ī default SMTP port 587 is the option to submit an email for routing. Later on, port 465 became obsolete and was revoked in favor of STARTTLS wrapper over SMTP. IANA registered 465 as an SMTP port, but it has never been recognized as an official SMTP transmission or submission channel. It was meant for the SMTPS encryption and authentication wrapper over SMTP. They usually prioritize secure connections like 587 or 465.Ĥ65 is not an RFC-compliant port. Cloud hosting providers and many email clients (Gmail, Microsoft Outlook, Mozilla Thunderbird, etc.) block port 25 to prevent spam. This is a standard port for relaying messages between email servers. Request to terminate the SMTP conversation Once the message contents have been transferred, a single dot must be sent in a line to terminate. Lets the client start the content transfer Initiates the transfer of the email contents including body text, attachments, and so on. (For multiple recipients, the command will be repeated for each recipient’s address) Says that a new mail transaction is starting and specifies the sender It identifies that the client uses the ESMTP protocol. The domain name or IP address is usually sent as an argument together with the command. EHLO is an alternative command to start the conversation. Identifies itself and initiates the SMTP conversation. Let’s take a look at the interaction between the SMTP client and server through a simple email delivery example:
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