How to manage mail queue in Plesk?
Step 1.Login on plesk panel & then click on “Tools & settings” which was at left sidebar.
Step 2. After find the “mail server setting” & then click on it.
Step 3. After click on “mail queue” tab & then click on clear.
Note:- If you cannot send e-mail through your mail server, this can mean that your mail server is overcharged and cannot cope with the amount of received messages. This can happen when somebody is sending spam messages through your mail server or the e mail-send daemon responsible for sending mail is down. In such cases, accessing the mail queue manually can help you to figure out and clear out the potential sources of such an issue.