After upgrading to 3.72 the bandwidth for only one website raised from max 2GB last month to 870GB for the last 3 days.
The whole bandwidth appears to be mail transfers, but there is no difference at mails/minute this week.
Also I checked the bandwidth on my router and the bytes transfered are far far below that number.
I also checked /var/log/maillog and there are only few lines fro this domain.
I recaclulated the bandwidth for this domain and it corrected the number for Saturday from 300GB to 676KB!!!! so the bandwidth dropped to 570GB.
Duling the last 2 minutes I'm writing this message the bandwidth raised from 570GB to 606GB (that is 36GB in 2 minutes) something impossible for my connection.