Bugs In the Mail App Can Lead To Data Loss In macOS Catalina

The developer of SpamSieve and EagleFiler plug-in for Apple Mail Michael Tsai, said in a blog post that those who upgraded to macOS Catalina 10.15.0 might suffer a data loss in Mail.

Tsai wrote that he had heard many users reported that when they upgraded from to Catalina from Mojave, the Mail app said that the process has succeeded, but in reality, lots of messages were lost or incomplete.

Other users even reported message loss when they move them from one mailbox to another. In a blog post, he said that if users move messages from one mailbox to another, with either AppleScript or drag-and-drop, what they get might be the emails with only the headers. In another situation when the messages are transferred to a server mailbox, from other devices, they will be seen as being deleted.

These problems are especially troublesome because Mac users may not know that something went wrong until they take a closer look at the affected mailboxes or messages. The problem can also spread to other devices because of the synchronization of data to the server.

Backups can be of little help here because the data of Mail changes constantly, and we have no straightforward way to merge messages of the latest backup with restored data.

Despite the difficulty, creating backups is still advisable. Apple Support is currently telling users that the Mail data that has been lost in Catalina cannot be recovered; however, Tsai said that this was not true. He said that to import them to Mail, users can access Apple Mail's File and then Import Mailboxes.

Tsai also wrote that he was not sure whether the problem is caused by bugs or any other reason. On Friday, macOS Catalina 10.15.1 beta was released to developers, but it is unclear if the bugs have been addressed or not.