Unless you are the recipient, you can’t check.
If you are, then you need to check the settlings and features for that acctount to see if any rules have been set up. They are in different places for different accounts providers. Most can not be changed on the iPad itself, but rather in the online settings for the account.
iCloud’s email rules are changed on the icloud.com site. Googles on their site. I’m not sure about other accounts.