DavMail should check Character validity while transfere Exchange calendar to Thunderbird, and best repair them.

[ifrh]

In the course of the discussion within a Thunderbird bug report regarding an XML parsing error of TB, it turned out that TB received invalid structures from DavMail. The cause, however, were forbidden characters sent by the Exchange. For example, null bytes within the structure without the XML string having been completed in terms of content and syntax.
DavMail could carry out “repair” measures here.

Reference : Thunderbird Bugreport https://bugzilla.mozilla.org/show_bug.cgi?id=1941840

I took a screenshot of WinMerge-Window, in which I had compaired the DavMail-Logfile with Thunderbird's Error-console, "Zerro-Bytes_in_VCALENDAR_entries_Bug"

[ifrh]

I did some programming, which fixed the problem for me. I will create a pull request.