The LetsEncrypt Root Certificate (DST Root CA X3) will expire on 30-Sep-2021. While there is a new Root Certificate available for a while, some devices and browsers might show an error after that date as they might not have got the new Root Certificate.
Here is the simplified overview:
Old LetsEncrypt chain:
DST Root CA X3 : Expires 30-Sep-2021
R3 (Intermediate): Expires 29-Sep-2021
New LetsEncrypt chain:
ISRG Root X1 : Expires 04-Jun 2035
R3 (Intermediate): Expires 15-Sep 2025
If Read more [...]
Exchange constantly writes DB Logs to disk. These logs only get cleared when a backup is done.
If you need to clear those logs without a backup, use the following commands (if the DB log files are on the d: drive):
Open a cmd box with admin rights
add volume d:
That's it. You should now have much more free disk space.