Exim provides a quick way to check the total number of mails in the queue. This is done using the exim -bpc Although, this is not the same for postfix. Postfix doesn’t come with an easy way to do that.
How to Check Total Number of Mails in Postfix Queue
A quick tip on what I use to check the postfix queue number is the following command:
# mailq | tail -n 1
-- 6899 Kbytes in 1518 Requests.
Basically, postfix returns the queue statistics at the end of the queue listing command. We are simply tailing that to find the number.