incoming emails going to the junk folder for all the users under our domain

Hello mushag 

I understand that incoming emails going to the junk folder for all the users under your domain

Since it is happening to all users I suspect it has to be an organization wide level troubleshooting, you need to pick a user (Maybe you if you are affected) get a sample email from the Junk folder and extract the message header use the Microsoft header analyzer https://mha.azurewebsites.net/ to check the following headers

use this link below to understand the scores

https://docs.microsoft.com/en-us/Exchange/antispam-and-antimalware/antispam-protection/antispam-stamps?redirectedfrom=MSDN&view=exchserver-2019

Then you can also do a message trace to see and check the message events 

https://docs.microsoft.com/en-us/exchange/monitoring/trace-an-email-message/run-a-message-trace-and-view-results

from experience, I suspect anti-spam policy

Goodluck Mate!