Sendmail is a popular Mail Transfer Agent (MTA) used for sending and receiving emails on Unix-like systems. The mail queue is a temporary storage area where emails are held before they are sent out. Checking the mail queue is important because it allows you to see if there are any emails that are stuck or delayed in the sending process.
There are a few different ways to check the mail queue in Sendmail. One way is to use the ‘mailq’ command. This command will display a list of all the emails that are currently in the mail queue. Another way to check the mail queue is to use the ‘sendmail -bp’ command. This command will display a list of all the emails that are currently being processed by Sendmail.