Hello everyone, I write to ask for your help and i hope my problem can help others that may be in the same situation. I have Ispconfig running on an Azure VM. Everything works fine except for the email because for some reason Hotmail (Live, outlook.com, etc.), Gmail and other big companies reject all my email due tu secutiry reasons. I've read that this is a problem with the fact that the cloud VM can easily change IP addreses or complex datacenter stuff. To solve this i used a Sendgrid free accoun wich gives me 12.000 email cuota to send monthly, i configured the account on Ispconfig relay options and works perfect, all email going from Sendgrid are well recieved. The problem came because one user got a virus (and it happened again a week ago) and started to send spam email from his own desktop Outlook. He sent 9.000 emails so the Sendgrid cuota was spent in 2 days. Now i have no relay and i have to tell my clients to try to send to emails not hotmail o gmail, etc. Until my Sendgrid cuota is renewed. My question is: Is there any way to limit bandwith for individual users or any way to detect this behaviour and block the account? Or does anyone know a better solution to this problem? Thanks very much and sorry for the english, it is not my native language.