MCMailErrorDomain error 1030. The Operation couldn't be completed

In on Mojave on an exchange account, I have been getting “The operation couldn’t be completed. (MCMailErrorDomain error 1030.)” for the last couple of weeks. If I click on an email, the error will pop up twice. Sometimes, it won’t error and sometimes it will.

When composing an email, I get an error.

After it sends the email, I get "The message “subject” could not be moved to the mailbox “work” An error occurred while moving messages to mailbox “”.

I’ve already disabled and re-enabled the account. I have also deleted the account and added it back. I’ve searched but couldn’t find anything useful. I tried to add a new SMTP but it didn’t seem possible for an Exchange account. I’ve tried rebuilding mailbox.

Please help with other ideas. Thanks.

since a few days I have the same problem.
Is there any solution?


Not that I know of. I went to the Apple Store and they suggested that I try a fresh install of the OS or try upgrading to Catalina. I decided to get MS Outlook for Mac and have been using that without much of a problem.