comsat is the server process which listens for reports of incoming mail and notifies users who have requested to be told when mail arrives. It is invoked as needed by inetd(1M), and times out if inactive for a few minutes.

comsat listens on a datagram port associated with the biff service specification (see services(4)) for one line messages of the form

user@mailbox-offset

If the user specified is logged in to the system and the associated terminal has the owner execute bit turned on (by a biff y), the offset is used as a seek offset into the appropriate mailbox file, and the first 7 lines or 560 characters of the message are printed on the user's terminal. Lines which appear to be part of the message header other than the From, To, Date, or Subject lines are not printed when displaying the message.

/var/adm/utmpx

user access and administration information

See attributes(5) for descriptions of the following attributes:

inetd(1M), services(4), attributes(5)

The message header filtering is prone to error.