Port 25 is the standard and default listen port for SMTP. This port is sometimes restricted by providers that wish to discourage email abuse or enforce authentication before sending. You can easily modify your settings to use an alternative port. We encourage port 587 which also requires authentication. Regardless of the chosen port, all MailChannels connection ports support TLS encryption and advertise this in their ehlo menu.
Supported Connection Ports
|25||Standard SMTP Port 25 - Supports STARTTLS encryption at ehlo.|
|2525||Alt Standard SMTP Port 2525 - Supports STARTTLS encryption at ehlo.|
Secure SMTP Port 465(Legacy Only) - RFC8314, Section 7.3. Port 465 has been reassigned. We continue to support legacy clients required to use port 465 but encourage all others to choose another port using TLS encryption.
"Historically, port 465 was briefly registered as the "smtps" port. This registration made no sense, as the SMTP transport MX infrastructure has no way to specify a port, so port 25 is always used. As a result, the registration was revoked and was subsequently reassigned to a different service."
|587||Standard Authenticated SMTP Port - Supports STARTTLS encryption at ehlo and requires authentication.|
For more information on the port 465 reassignment by IANA, please refer to IETF.org - RFC8314.