Port 25 is primarily used for SMTP relaying, which is the transmission of email between email servers. According to research, SMTP port 25 continues to be used primarily for SMTP relaying (sending email from one email server to another). This is a critical function for ensuring email reaches its intended destination.
In more detail:
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SMTP Relaying: Port 25 facilitates the communication between mail servers, allowing them to forward email messages across the internet.
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Server-to-Server Communication: This port enables email servers to exchange email, routing messages towards the recipient's mail server. Modern email clients (like Microsoft Outlook, Mail, Thunderbird, etc.) do not directly use port 25 for sending email; instead, they typically use ports 587 or 465. Port 25 is mainly for server-to-server communication.
In summary, while end-user email clients now prefer different ports for sending mail, port 25 remains vital for the underlying infrastructure that ensures emails are properly routed and delivered across the internet.
