Overview
After December '21 Update (21.12.10943.6), External Mail Sources have a separate key in the registry for logging purposes. If you bump into issues that are related to Mail Sources (some object/email not coming in, connection not establishing, ...), one possibility is to enable this logging to show details regarding that process.
Solution
Open Registry Editor on server and edit registry keys to these following values and reproduce the issue after that (note that it may not exist so you may have to create it):
HKEY_LOCAL_MACHINE\SOFTWARE\Motive\M-Files\<MFVersion>\Common\MFExternalMailSource\Logging
"LogDir"="%TEMP%\MFilesLogs"
"FlushIntervalInSeconds"=dword:0000000a
"EnableVerboseLogging"=dword:00000001
"LogCategories"=dword:ffffffff
"TotalMaxSizeInMB"=dword:000000c8
"DeleteLogsOfOtherInstancesAfterDays"=dword:00000015
"PreserveAtLeastDays"=dword:00000000
"Enabled"=dword:00000001"
There is no need to restart any services after altering these registry settings. By default, the location of these log files is %TEMP%\MFilesLogs (in a standard environment: C:\Windows\Temp\MFilesLogs).
Remember to change the value for Enabled back to 0 after the issue has been reproduced.
When you have sent the log files to M-Files, consider deleting the log files to free up disk space.
Important Note:
When sending the logs (or any other sensitive data), please make sure to use Cryptshare Web application that allows easy and secure exchange of sensitive information. See instruction here: /article/How-to-Send-Files-via-CryptShare-Portal
