The barrier to hosting your own email is that you'll spend a day configuring everything, and a year later, the big providers will slightly change a spam detection algorithm, your mail won't be delivered, you won't know, and there will be bad consequences for you.

The barrier to changing your git origin is spending five minutes setting up an account and repo somewhere else. Everything will work absolutely fine, you'll still have all your git history, you'll just be slightly less discoverable and some potential contributors might not want to create an account.