Apple Mail bug causing data loss in macOS Catalina

What you need to know

  • Report suggests Catalina may be experincing data loss issue within Mail App
  • Moving emails between inboxes can result in blank messages which are eventually deleted.
  • Data store failing to pull large numbers of messages from Mojave to Catalina.

A blog post by Michael Tsai via MacRumors is today suggesting that macOS Catalina seems to be experiencing a data loss issues.

According to the report, users on macOS Catalina 10.15.0 (build 19A583) are reporting problems when updating Mail's data store from Mojave to Catalina, and when moving messages between inbox.

According to Tsai, he's heard from several users that updating Mail's data store from Mojave to Catalina sometimes says that it has succeeded, when in fact on closer inspection it turns out that large numbers of messages are incomplete or missing entirely.In addition, users have reported the loss of message content when moving emails between mailboxes. From Tsai's post: Moving messages between mailboxes, both via drag-and-drop and AppleScript, can result in a blank message (only headers) on the Mac. If the message was moved to a server mailbox, other devices see the message as deleted. And eventually this syncs back to the first Mac, where the message disappears as well. Tsai warns that these issues are particularly pernicious because users may not realize anything's wrong unless they look at affected messages or mailboxes. Since the data is synced to the server, these problems can also propagate to other computers and devices, and relying on backups is difficult because Mail data is continually changing and there's no easy way to merge restored data with messages received since the last backup.

So not only is data store failing to recover large numbers of messages, moving messages between inboxes appears to be turn some emails into blank messages. When devices on your iCloud see these blank messages they delete them, which in turn results in the message being deleted on your Mac as well.

The report notes that the best defence against this currently (apart from not updating to Catalina) is to ensure you have a Time Machine backup of all your Mail Data.

Tsai notes that Apple Support appears to be erroneously advising users that lost Mail data in Catalina can't be recovered from a Time Machine backup made using macOS Mojave. According to Tsai, this is not the case: Apple Mail's File -> Import Mailboxes... menu bar option can be used to selectively import them into Mail in Catalina as new local mailboxes.

It is unclear at this stage whether Catalina 10.15.1, released in beta form on Friday to developers, has resolved this issue. In the meantime, anyone who relies on Apple's Mail App is strongly advised not to upgrade to macOS Catalina.

Stephen Warwick
News Editor

Stephen Warwick has written about Apple for five years at iMore and previously elsewhere. He covers all of iMore's latest breaking news regarding all of Apple's products and services, both hardware and software. Stephen has interviewed industry experts in a range of fields including finance, litigation, security, and more. He also specializes in curating and reviewing audio hardware and has experience beyond journalism in sound engineering, production, and design.

Before becoming a writer Stephen studied Ancient History at University and also worked at Apple for more than two years. Stephen is also a host on the iMore show, a weekly podcast recorded live that discusses the latest in breaking Apple news, as well as featuring fun trivia about all things Apple. Follow him on Twitter @stephenwarwick9

9 Comments
  • A little late for that recommendation...
  • The blog post was today, iMore literally couldn't have posted this sooner
  • Umm...yah, I get that, Danny. The way it was worded made it look like they were....here, try this: "Today Ford announced a recall on their new Mustangs due to a faulty brake system. Anyone who relies on the new Mustang's brake system is strongly advised not to buy a new Mustang." Kinda silly/obvious, no?!
  • Might be obvious to most but some people will continue to use the thing with the problem which is why these recommendations go out. It's a pretty bad bug from Apple, I can't defend them on this but it's really odd how it didn't get noticed in the public betas
  • This bug was reported to Apple when Catalina beta 5/6 was released.
  • Then this is a bad mess up from Apple, hopefully they will learn from it (though, maybe not)
  • This is the most detailed description of a missing data in Mail issue, but I agree - the general issue of Mail losing data in Catalina has been around ever since ship day, but none of the pundits thought it was reason enough NOT to upgrade. I thought it serious enough to turn off all auto updates on my Macs. And will be waiting until the community judges the issue fixed, not Apple says it's fixed. I've been suffering blank emails in my In Box in Mojave, long before Catalina shipped. Spreads like a virus, initially other devices have the body of the message, then gradually, they lose it too. All still in the In Box. And I tried all the usual tricks to re-download the message. All except, delete the mailbox and re-add it - thought better not to tempt fate.
    I ran none of the betas - not touching that **** this year - and my 2018 Mojave MacBook 15" can't manage to get the body of an email for me! This is serious.
  • Again, why does ANYONE install/use the x.0.0 version of an OS? Of COURSE there are going to be problems.
  • Technically x.0 releases have many issues that don't always get picked up in the betas because even the public betas don't have nearly as many users as when it goes fully public, which means technically someone has to be the x.0 guinea pig to report these issues, otherwise they'd be in the x.1, unless Apple was aware of it and decided to release anyway, which is seemingly true with this one according to nekton123's comment