As someone else mentioned here, the only risk is that spammers will blacklist mnesty.com .
There should be some type of domain rotation (or you can test spoofing, just to see if spammers use the same anti-spoof software everyone else does), just like how spammers do so.
As an aside, kudos for using gitlab instead of github.
If and when that happens, someone can pick up a suite of cheap domain names. Thanks to the proliferation of generic TLDs, you can register a domain for less than a dollar per year through a legitimate registrar.
There should be some type of domain rotation (or you can test spoofing, just to see if spammers use the same anti-spoof software everyone else does), just like how spammers do so.
As an aside, kudos for using gitlab instead of github.