Twice in the last month, it seemed like I wasn't getting any emails for several days, then suddenly it downloaded all of them at one time, then went back to checking and downloading every 10 minutes like it is set to do. It seems to occur randomly, and I can not find any troublesome emails in the server view (Zoho) that might have caused issues. And even if there were, it downloaded and went back to normal without me doing anything. The first time was over a week, and the second time was 3 days. I have checked that nothing is wrong with the settings. Also, there are 2 Zoho accounts being downloaded through Thunderbird, and this glitch only affected one of the accounts and not the other. At this point, I'm scratching my head and not sure what to check next. I never got any kind of error message letting me know something happened; I only know when I suddenly get 40 backlogged emails at one time!