What are the risks involved in excluding a file/folder?

I am using Bitdefender Total Security 2020. It quarantines my Thunderbird's INBOX file, if there is any virus in an email. For a single virus it quarantines the entire INBOX mbox file which contains all the email with in it. So, I would like to add the Thunderbird's profile folder to exclusion list.

1. what are the risks involved in excluding a file/folder?

2. I know that if I exclude any folder, here the Thunderbird profile folder,then it will not be scanned for threads and it will be excluded from active shield protection. So if any virus comes as an attachment file inan email will not be removedby BD. But it will be removed immediately if I download the attachment file to any other location. Apart from thisare there any other risks involved?

3. Can a virus within the INBOX mbox file, affect the other files in the PC, from being there?

4. Can any other virus (except the virus in the attachment file) come into the excluded folder from outside?

5. If any unwanted program or any other virus makes any changes in the files of the excluded folder, then what happens?