cyrus auto-generated failure message from address

[marc.bigler at day.com]

Hello,

When Cyrus generates a failure message for example because someone sent a
mail to an unexisting IMAP account then that auto-generated mail contains
the following From header:

From:   Mail Delivery Subsystem <MAILER-DAEMON at unspecified-domain>

As you can see the domain is "unspecified-domain" and I wanted to know if
it is possible to change that ? if yes where ?

Thanks