An SMTP queue is a holding area for emails that are waiting to be sent. When you send an email, it is first placed in the SMTP queue. The SMTP server then attempts to deliver the email to the recipient’s email server. If the recipient’s email server is unavailable or busy, the email will remain in the SMTP queue until it can be delivered.
There are a number of reasons why you might need to check the SMTP queue. For example, you might need to check the queue to see if an email has been sent, or to see if an email has been delayed. You can also check the queue to see if there are any errors that are preventing emails from being sent.