This problem occurs when two or more fields have the option “Append Changes to Existing Text” activated in the SharePoint list and one of those fields is mapped to the E-mail thread.
When E-mail Converter tries to update an item for a mapped thread field, all other fields with the option “Append Changes to Existing Text” selected get updated too.
To avoid the problem, disable “Append Changes to Existing Text” for other fields:
Open the SharePoint list which is mapped with E-mail Converter.
Click on Settings > List Settings
Open all possible multi-line columns to check which one(s) has the” Append changes …” activated besides the e-mail tread column. Disable “Append changes …” in all but the e-mail thread column.
