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Beware Mail Data Loss in Catalina

Mail 13.0 About boxMichael Tsai, the developer of the long-standing SpamSieve plug-in for Mail on the Mac, has written a blog post warning about potential Mail-related data loss when upgrading to macOS 10.15 Catalina. In particular, he’s hearing from numerous customers that updating Mail’s data store from Mojave to Catalina sometimes says that it succeeded, when in fact, large numbers of messages turn out to be incomplete or missing entirely. Plus, moving messages between mailboxes on the Mac can delete message bodies, leaving only headers. If you moved the message to a mailbox on the IMAP server, other devices see it as deleted, and that deletion status eventually syncs back to the original Mac, where the message disappears as well.

As Michael Tsai points out, these problems can be difficult to notice (if you’ve already updated to Catalina, run through your mail to see if it has been affected), the problems can propagate to other devices, it’s difficult to make a complete backup, and even if you have a backup, it’s hard to restore.

To reiterate our advice in “macOS 10.15 Catalina Ships, Upgrade with Caution” (7 October 2019), hold off on upgrading to Catalina for a while, particularly if you use Mail.

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Comments About Beware Mail Data Loss in Catalina

Notable Replies

  1. Using Mail with Gmail, IMAP always behaves a bit strangely; and Mail under Catalina does add a few more quirks. The main one I’m seeing is that a mail item moved from one mailbox to another copies rather than moving, leaving the original to be manually deleted. Annoying but not fatal— I’m not losing any mail bodies, I’m glad to say.

  2. It’s worse than that, because you should be able to specifically target the Data volume to fix whatever problem led you to fsck in the first place, and the Mac-Enterprise list indicates that doesn’t work either. (And in theory, the read-only volume should have no such problems, so it’s there or something else entirely.)

  3. I recommend Mail Steward for archiving emails before a major OS update. It stores emails in a MySQL database that cant be touched by the OS installation. I have emails going back over 15 years.

  4. No data loss here, but a different problem: out of application memory crashes when Catalina was upgrading its Mail from my Mojave installation. Running 16 GB RAM, that shouldn’t happen but with Catalina it did. Reason: I have nearly 20 years of old emails stored in mailboxes “On My Mac.” This is the first upgrade when I’ve run into the problem. I did find a work-around that I’d be glad to share if anyone wants to know, but I’m also looking for a solution that would keep some of those emails outside the Mail program without turning them into textfiles while having them ready to bring back into Mail in Catalina and future Mac OS as well.

  5. PS: Mail Steward could be the longer-term solution I’m looking for, of course. I’ll check it out.

  6. Wait… is this the opposite of Sherlocked when a OS upgrade makes a 3rd party app more necessary?

    This app has been stewarded by Apple.

    Thanks Apple.

  7. Catalina has also introduced the issue where 3rd party programs (such as HoudahSpot or BusyContacts cannot search Apple Mail. (I have registered my view on For this reason I am researching 3rd party mail programs such as Mailmate or Postbox. Any opinions or comments on what 3rd party mail apps are worth looking at… Thanks

  8. I swear by InfoClick. Use it multiple times every day.

  9. I have to admit, I’ve never had a problem searching for mail and my email, stored in mail boxes on “on my mac” goes back decades.

    What problems occur that require a 3rd party search engine for mail?


    Al Varnell

        October 16

    Any opinions or comments on what 3rd party mail apps are worth looking at…

    I swear by InfoClick. Use it multiple times every day.

  10. David, I agree, Mail search is very good. But I like HoudahSpot as it allows me to create a search then save it to the Finder (like a smart mailbox). I have lots of these, which I can then search for. I don’t think I can do this with Smart Mailboxes in Apple Mail (also when you have 100s of smart mailboxes it gets a bit messy!)

    Thanks Al for InfoClick I’ll check this out as it appears to build its own index (so independent of Catalina’s restriction). I could not tell if it allows me to save a search to the Finder & then run the search by launching from the Finder (I’ll download the trial & test this…)

  11. DEVONthink Pro will archive individual emails, entire mailboxes, or multiple mailboxes with a single menu command. They remain in EML format, as originally organized, with all metadata including MailTags. You can update the archive whenever you wish and DTP will not import duplicate UUIDs. Anything indexed in DTP is also indexed in Spotlight, unless you opt out. Of course, DTP will also file your other documents and perform all sorts of tricks. 15% discount for TIDbits members.

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