Within home lab exchange stopped mail flow (in and out) due to disk space issue. Had to do some clean up and used a script as well to free up space. Now the mail flow is back to normal and everything is working fine.

I was not aware that exchange mail flow will stop when the space is below 30GB. I thought, I had enough space but not the case. Now, I have enough space to handle the database for at least 1-2 years.