The way we handle this in our community is by copy/pasting the email into a reply on the forum. In some cases we write in our own name and mention who we are quoting, and then email the person back to let them know and with the link to the topic. In others we post it and then change the author to the person who sent it (requires admin privileges). It’s a bit longhand but is safest, in my humble opinion.
We also often start personal messages (tickets!) to people who email us, creating staged users. That works very well for responding to received emails and then following up.