A Mail Alias is a mapping of an email address with a given Odoo Document
model. It is used by Odoo's mail gateway when processing incoming emails
sent to the system. If the recipient address (To) of the message matches
a Mail Alias, the message will be either processed following the rules
of that alias. If the message is a reply it will be attached to the
existing discussion on the corresponding record, otherwise a new
record of the corresponding model will be created.
This is meant to be used in combination with a catch-all email configuration
on the company's mail server, so that as soon as a new mail.alias is
created, it becomes immediately usable and Odoo will accept email for it.