print the mail queue
mailq [-v]
The mailq utility prints a summary of the mail messages queued for future delivery.
The first line printed for each message shows the internal identifier used on this host for the message, the size of the message in bytes, the date and time the message was accepted into the queue, and the envelope sender of the message.
The second line shows the error message that caused this message to be retained in the queue; the error message won't be present if the mail message is being processed for the first time. The remaining lines show message recipients, one per line.
Note that mailq is identical to the command:
sendmail -bp
sendmail, /etc/aliases file
Sendmail by Bryan Costales, O'Reilly & Associates (ISBN 1-56592-056-2)