To help protect our mailservers from misuse and to mitigate the possibility of them being blacklisted we have a number of security measures in place one of which is an automated process that will temporarily disable a mailbox from sending if certain behaviours are seen. This does not necessarily mean the mailbox has been compromised but behaviours such as large numbers of IP addresses logging in and sending mail, high volume of email with spam-like characteristics (HTML email with just images and links for example) or a large number of bounceback messages can trigger this process.
Depending on the reason that sending has been disabled this cab either be a temporary 24-hour hour block or a more permanent block that can be lifted once the mailbox is secured. If you see this error please run a virus scan on the machine that you use to access this mailbox and then reset the mailbox password through you hosting control panel (guide here). One done raise a ticket to our support team providing the results of the scan, the name of the affected mailbox(es) and confirm you have reset the password and we can then check and reactivate that mailbox for you.
