We can disable a mailbox for a few different reasons outlined here on our Bulk email policy, and AUP:
The first type of disabling is done automatically, when our servers sense that a user is sending messages beyond the maximum bulk email limit. When this is done, a disable notification is sent to the listed AUP contact along with information regarding why the mailbox was disabled.
The second type of disabling is done automatically, when our servers sense that a user is sending messages with spam content. In this case, a notification regarding the disabling of a mailbox and the details of the spam being sent are given to the listed AUP contact. This and the following type of disabled mailbox typically indicate that the mailboxes password was most likely compromised and being used by a spammer to send messages from our SMTP servers. We recommend to simply change the mailbox's password to a strong value, and scan any associated computers for viruses and malware.
This will ensure that the user's mailbox is not continuing to send spam and is not re-compromised after updating the password. After these items have been addressed, we can re-enable the mailbox for use.
The third type of disable would be done manually based on feedback given to our AUP team indicating that spam is being sent from mailboxes that reside on our servers. This type of spam does not specifically violate the bulk email limit and also passes under our automatic spam checks. When our AUP team receives notification of this activity, we manually disable the mailbox in order to discontinue the use of our servers from sending spam, which hurts our reputation and thus, your domain's sendability. When we manually disable a mailbox, no notification is sent to an administrator at this time, but we are working on a solution for the future, that will allow notifications to go out when mailboxes are disabled based on feedback from the recipients of messages sent from our servers. Often times, messages are reported to our AUP team several days later, even after the password has been changed. When this happens, you may see mailboxes continue to become disabled even after changing the password and checking any associated computer for viruses and malware. This is because the disabling process is done manually at the point in time in which we receive notice. We recommend to simply update the password once more, to a new value, and re-enable the mailbox.
We are currently working on a way to automate the 3rd type of disabling to include a notification sent to the listed AUP contact. Thanks for your patience while we improve our process to better serve your needs.
If you would like more information regarding which activity the mailbox was disabled for, we can provide you with some details of the outbound message activity within the past 7 days per our SMTP logs.
We thank you for your understanding of this difficult situation. We do try to keep your best interests in mind, while also protecting our servers and resources from blacklisting or poor reputation.