A month ago we have a new dedicated server. In order to fight against Spam and to be able to offer a quality service, we always contract, in addition to a main IP, 16 IPs plus to distribute among the clients domains that we manage.
As soon as these IPs were assigned to us, we could see at https://ipremoval.sms.symantec.com/lookup that they all had a bad reputation: snow shoe spamming and unauthorized to send emails.
With effort, we have left all the lists, not all our IPs were listed in your list, some were left, until today.
When everything seemed to be good, yesterday around 23:00 I saw an alert: more than 800 emails per hour!
Stopped the attack, today it was solved: a virus infect client computer, obtained the key, sent Spam and put redirection rules in RoundCube to find out everything... in 6 accounts configured in outlook! i have no luck :(
Just two days ago I sent an email to investigation@review.symantec.com but still no response. Meanwhile, several important emails did not reach their destination. With the exception of yesterday's incident, we failed to see the problem and therefore the solution.
Could you help me understand what is happening and help to solve my problem?