Hello, I am using ISPConfig to deliver some email notification only. Probably only 5-20 email per day at maximum, and it's not everyday sending the same amount. However, recently i noticed that the server is not responsive enough and i saw many mail queue, for example like this: DAF1422974* 601 Wed Jun 14 11:33:31 noreply@mydomain.com julianneconcel@yahoo.com DD3F5229A8* 589 Wed Jun 14 11:30:20 noreply@mydomain.com irisol65@yahoo.com 15FE22296E* 615 Wed Jun 14 11:15:59 noreply@mydomain.com allisonmendezraudales@gmail.com 7EE5922994* 591 Wed Jun 14 11:25:06 noreply@mydomain.com carlenemack02@gail.com B91A222979* 603 Wed Jun 14 11:28:34 noreply@mydomain.com jessicablondell@gmail.com 864DB229A1* 589 Wed Jun 14 11:28:13 noreply@mydomain.com fcurtis3465@gmail.com 2D21F229A6* 595 Wed Jun 14 11:29:51 noreply@mydomain.com brandiclmns@gmail.com 8B19722984* 593 Wed Jun 14 11:21:03 noreply@mydomain.com jefhiggs18@gmail.com 7197022985* 589 Wed Jun 14 11:21:18 noreply@mydomain.com sadecooper865@att.net i do now know those email, and never send to those email at all. i tried to like delete all the queue, but it will come again in just a few minutes. I received it more than 500 queue on my server. I am using debian 10, with installation https://www.howtoforge.com/perfect-server-debian-10-buster-apache-bind-dovecot-ispconfig-3-1/ Please advise, what should i do to prevent this? Thank You.
Examine those e-mails in the queue, my signature has link to e-mail tutorial, it has info on troubleshooting. Try to find what is sending those e-mails, it may be an e-mail account with password known to third party that sends spam, or a script on your server that sends those e-mails.