Self-Disabling email accounts

Self-Disabling email accounts

Hi folks,
I have 4 mail accounts set up within Zoho Mail. Every couple of days or so, I spot that 2 of them suddenly aren't showing any new incoming mail. When I check under Settings, I find that those two have the slider 'Enable / Disable the account' toggled over to disabled. 

I can re-enable them okay, and then they start working, but I have to keep doing this manually, every few days once I've spotted the problem, and it's quite disruptive. It slows up my email / business and drives me mad. The other 2 accounts work fine and never have a problem.

Anyone any idea what the problem is and / or how to prevent it happening again?

Many thanks,
Jon