Vendor Name: OnePlus
Device name: OnePlus 6
Device CodeName: enchilada
Version of /e/OS or Stock which existed previously: /e/OS T 1.17
Is the device Rooted / Not rooted: Rooted (Magisk)
Unfortunately, I am also affected by the e-mail app bug. As a workaround, I have installed K9, which can be found on F-Droid (and App Lounge, of course). Still, I hope that this problem will be fixed soon.
EDIT: I decided to not only delete the cache, but also the internal storage of the /e/OS e-mail app and added the accounts back. I will see whether this fixes the problem.
I have also noticed that the browser has not been updated and is still on Version 117. Still, there is hope that this will be addressed in the next release.
(IMHO: This should be automated as much as possible - the browser is critical and should be kept up-to-date.)