Check What Mail are Quarantine by Spam filtering
This link you can see what e-mail quarantine by spam filtering, you can click this message and take the action such as preview, download or release the message, by default the quarantine item will automatically remove on 30 days.
How to add the e-mail/domain to bypass the Spam Filtering
Step 1: Go to Admin Center > Exchange
Step 2: Protection > spam filter > click “Edit”
Step 3: spam and bulk actions, you can adjust the Spam filtering level and action!
Step 4: Click “allow lists” you can add the sender (e-mail address) or domain to bypass the spam filtering