On the plus side, since it's all pretty fresh - you can do things like "MUST be DKIM signed from an aligned reverse DNS" on IPv6 and have a chance of it working.
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.
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.