We have 3 devices (MacBook Pro, iPad, iPhone) all accessing the same email address. We have been in contact with you previously as we have been having issues for the last 10 days which have not been resolved and stemmed from us adding an existing mail account on a new laptop. It seemed that the use of 3 devices might be causing the problem although it appeared that there was no issue when the old laptop was being used. In order to allow all the blocks from yesterday to clear, the laptop wifi was switched off overnight. Having retried to use mail this morning, the account used (praoffice.com) connected on switching on wifi and downloaded messages but was then immediately blocked so we know the settings are correct. We have tried your previous suggestions for resolution but are no further forward. Why is our IP address being so readily blocked? I need to know what can be done about it as this is affecting my business activities (I appreciate the global issues with cyber security last week and that you have been trying to get back to normal) but please help!

This is very likely caused by the Notes app on the Mac, not your passwords or mail settings.

When Notes is turned on for an email account, it opens several connections at once and cancels some of them partway through signing in. The mail server counts each cancelled sign-in as a failed login, and after enough of them in a short time it blocks your IP address for an hour. Because the block is on the IP address, every device on the same internet connection loses email at the same time. That's why the iPhone and iPad stopped too.

Turning Notes off for the account on each Mac should stop the blocks:

1. Open System Settings > Internet Accounts.
   
2. Select your email account.
   
3. Turn off Notes and leave Mail turned on.
   

If you're already blocked, it clears by itself within an hour. Any notes already stored in the account aren't deleted and will come back if you turn Notes on again later.