SMTP ports

MailChannels Outbound Filtering listens on the following ports. All ports support STARTTLS encryption.

Port	Description
`25`	Standard SMTP. Preferred. Sometimes blocked by hosting providers.
`587`	Standard authenticated SMTP. Requires authentication. Use this if port 25 is blocked.
`2525`	Alternative to port 25. Commonly used on cloud platforms such as Azure that block port 25 on VMs.
`465`	Legacy SMTP over SSL. Supported for older clients that cannot use STARTTLS. Not recommended for new configurations — see RFC 8314.

Port 465 was briefly registered as smtps but the registration was revoked and the port reassigned. MailChannels continues to support it for legacy clients only.

If port 25 is blocked in your environment, use port 587 or 2525. Both are configured identically to port 25.

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