Is there a way to set it up so user@example.com can be a lemmy account and also a mastadon account? I seen people using subdomains like user@lemmy.example.com and user@mastadon.example.com is this nessasary? Could u also set up a matrix account with the same user@example.com? If not what woukd be requured to change to make this possible?
Technically you sort of can do that with email. Most providers let you verify you own the other email and then use the other provider’s SMTP to send from a different address.