This might not be necessary depending on when Avanan was integrated with the 365 environment. Avanan no longer creates an admin user as of Early/Mid 2022.
If you do not see an Avanan user, move on to step 2.
Go to “Active users” in admin console:
delete admin user:
Step 2. Rules
Go to “Admin Center” → Exchange.
Mail flow → rules
You should delete 3 rules (in case you have created inline rule):
Avanan - Protect
Avanan - Junk Filter
Avanan - Whitelist
Step 3. Connectors
In “mail flow” → connectors, you should delete 3 connectors (or 2 if you didn't create an inline rule):
Avanan Inbound.
Avanan Outbound (is created when you create inline rule).
Avanan Journaling Outbound.
Step 4. Journal rule
Go to “Compliance management” → Journal rule:
Delete journal report email:
Delete Avanan - Monitor rule:
Step 5. Connection filter
Go to protection → Connection filter
Open “Default” rule, and from connection filtering delete the IP address.