Queue Limits

As stated earlier, the default maximum time that an undelivered mail message is queued is three days. If your system is disconnected for longer than three days, mail will be returned to the sender. You can change the maximum queue time by changing the following lines in the /etc/mail/sendmail.cf file from:

# return queued mail after this long
OT3d

to:

# return queued mail after this long 
OT999d

In this example, mail will be queued for 999 days before being returned to the sender. See the sendmail man page for a more complete explanation of the values for the queued mail timeout parameter.