MX

Mail Exchange (MX) is the "incoming" email server that accepts emails on behalf of a specific domain name using the SMTP protocol.

The MX server for a domain is resolved using DNS, and the MX server always runs on port 25.

• gmail-smtp-in.l.google.com for gmail.com
• example-slug.mail.protection.outlook.com for example.com using MS365
• inbound-smtp.eu-west-1.amazonaws.com for AWS Workmail
• etc