[LeonM]

> It's pretty bad - nobody is really doing it.

I'm curious how you came to that conclusion.

Messo's question above made me curious, so I just did a quick query on the database of Mailhardener. >99% of email coming from Gmail is delivered over IPv6 (from ~10k samples).

This appears to be provider specific though. For example: Yahoo seems to mail exclusively over IPv4, Zoho also IPv4. Most exchange based services appear to prefer IPv6. Microsoft 365 also uses IPv6.

So your conclusion doesn't really reflect what I am seeing in our database. Obviously, we process mostly DMARC reports, so maybe regular email is more IPv4 biased to support mail services that are not IPv6 capable.