The University's mail relay service is provided by oxmail.ox.ac.uk . This system acts in one of two roles.

Mail Exchanger
A mail exchanger is responsible for receiving the mail destined for a mail domain. DNS MX records describe the exchangers linked to each domain. When oxmail acts as an MX it is normally receiving mail from servers outside Oxford.
Smarthost
A smarthost delivers mail on behalf of other mail servers. It makes the routing decisions and handles any errors that arise. Oxmail only acts as a smarthost for Oxford mail servers.
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