Chapter in this post:
If you are about to upgrade your Mac to macOS 10.15 Catalina, you should definitely make a backup in preparation. Because when you update your Apple Mac to the new operating system, it can happen that some or all of the emails in the Mail app are lost. And even if the emails are picked up, they can be incomplete. Details about the problem and possible solutions can be found in this little guide.
This problem isn't all that new, but it's quite annoying when you work on a Mac. After all, many users depend on smooth e-mail traffic. If all messages are no longer available or no longer available after upgrading the Mac OS, valuable hours are lost in solving the problem. The developer Michael Tsai, among others, points out the errors and problems with the Apple mailing client in his Blog to (translated):
Here in the blog you will find a collective article on the currently known or most frequently documented problems that can occur after a Mac upgrade from Mojave to Catalina. I try to keep this post up to date and quickly incorporate new problems and proposed solutions. There are currently three entries for problems with mail under macOS Catalina:
For further coordination in the article, please use the table of contents "Chapter in this article" attached at the top. This allows you to quickly and easily jump to the desired subheading and the information below. I try to activate and answer comments and questions as soon as possible - but this can take a while depending on the volume;)
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.