Mail is disappearing, showing up in wrong folders, trashed mail is returning

Mail is disappearing, showing up in wrong folders, trashed mail is returning

Zoho Mail worked great for 6 months. Now all of a sudden, mail is vanishing—a lot of mail! Mail I deleted is coming back to my Inbox. Mail I read in my Inbox is missing, but shows up under Views; All Messages. I read my mail with Apple Mail and never had an issue whether I check it on my Mac or iPhone. Now it can't be trusted. I rely on email for business and I am at my wits end. Please help.