[feat] Add txt-record encryption

[mstaal]

Describe the feature

As discussed in forwardemail/free-email-forwarding#251, there should be an alternative to exposing email addresses in public DNS records.

This issue seeks to open this conversation again in the correct repository.

Checklist

• I have searched through GitHub issues for similar issues.
• I have completely read through the README and documentation.

[titanism]

Expect an update soon!

[titanism]

Hi folks 👋 We now support encryption on TXT records for free! 🎉 🚀

As of today we now allow you to encrypt records even on the free plan at no cost. Privacy should not be a feature, it should be inherently built-in to all aspects of a product. As highly requested in a Privacy Guides discussion and on our GitHub issues #254 and #251, we've added this!

Visit https://forwardemail.net/encrypt or click the "Encrypt Plaintext TXT Record" link in the nav/footer of any page on our site. We've also mentioned this tool in our FAQ as well.

Behind the scenes we encrypt your input with ChaCha20-Poly1305 and then convert it to a Base64 string.

Thank you for your patience, we've been hard at work! Our IMAP/POP3/CalDAV service is snappy now – and we're going to integrate iOS Mailbox IMAP Push support sometime soon too.

Here is a screenshot of the encrypt plaintext TXT page in action:

[Lordfirespeed]

It would be really awesome if we could get some more detailed docs on how the encryption works - especially how the encryption secret is kept secure 👀