Mail Keychain keeps popping up

Whenever I uses the mail app on my Mac, it asks me to enter username and password for "mail keychain" and after entering, it will pop up again when I write email, like once every 5 seconds, and after sending an email, it pops up many times, after entering one by one. I like using the mail app but have to switch to web outlook. Is there a way to disable this or fix this?