Due to the way POP3 is designed, it is impossible to be logged into the same mailbox with two separate sessions at the same time.
If your mail client is checking for new emails too frequently, it starts to open a new session before closing the existing one, and locks you out of your mailbox until the server can be certain there are no connections open to the mailbox.
This primarily happens if you attempt to log into your mailbox less than two minutes after your last login. If you set your mail client to connect less frequently, this problem should disappear.
If it is still occurring, make certain you have only one machine checking mail at the same time, as it may be that your other device (such as your phone, laptop, or home computer) is also attempting to download your email.
And if you are still having your mailbox locked, please raise a Support Ticket with our Customer Services team to make certain there are no external factors.
Article ID: 256
Created On: Fri, Mar 13, 2015 at 11:49 AM
Last Updated On: Thu, Apr 23, 2015 at 11:37 AM
Online URL: https://www.heartinternet.uk/support/article/why-is-my-mailbox-saying-that-it-is-locked.html