MAPI is broken in TB 60.5.2:

https://support.mozilla.org/en-US/questions/1251452

TB 60.5.1: http://ftp.mozilla.org/pub/thunderbird/releases/60.5.1/

How about a version 60.5.3 to really fix it. How do you roll it back using the FTP'd files? No real help for me with remote office installations without any tech support.

Download the installer for TB 60.5.1 from the provided link, e.g. the US English version for windows is here. Install over your existing version and disable automatic updates from Tools/Options/Advanced/Update. The profile folder with all your data is unaffected.

Thank you for the quick response - It's working

This worked on my Windows 10 machines, but on my Windows 7 machines I'm getting crashes with 60.5.1 when I try to send an email from another application.

ajtv said

This worked on my Windows 10 machines, but on my Windows 7 machines I'm getting crashes with 60.5.1 when I try to send an email from another application.

Update to 60.5.3 and see if it still crashes.

https://www.thunderbird.net/en-US/thunderbird/all/

Ok thanks. The 60.5.3 update appears to have fixed it.

A side note: the computers where I downgraded to 60.5.1 and disabled automatic updates seemed to update later anyway (from 60.5.1 64-bit to 60.5.2 32-bit for some reason).

ajtv said

Ok thanks. The 60.5.3 update appears to have fixed it. A side note: the computers where I downgraded to 60.5.1 and disabled automatic updates seemed to update later anyway (from 60.5.1 64-bit to 60.5.2 32-bit for some reason).

Check that you don't have a security program (Kaspersky, Avast etc.) that updates other programs irrespective of the update settings in e.g. TB.