IPv6 with Android Mail App

We recently noticed a problem with the “Mail” app on Android phones failing to send mail when the phone has an IPv6 connection (either via Wi-Fi or 4G LTE). The problem was traced to the Mail app sending an improperly formatted IPv6 literal in the EHLO command. We’ve updated our outbound mail service to account for this discrepancy.

RFC2821 defines and IPv6 address literals as such:

address-literal = "[" IPv4-address-literal /
                      IPv6-address-literal /
                      General-address-literal "]"

IPv6-address-literal = "IPv6:" IPv6-addr

The Android Mail app is omitting the “IPv6:” string in its literals.

5 replies on “IPv6 with Android Mail App”

Ah, excellent. I didn’t dig into it, but I did notice “some weirdness” recently with mail on my phone when I started to switch over to IPv6.

I’ve backed off pending some other work, but will be redoing the migration again in a few weeks.

Great service!

We have IPv6 in our office, but there were some issues with the old AP I was using for mobile device testing (an HP AP420) and at the time I assumed it was related to that since it the AP was flaky with handling IPv6 traffic. I recently replaced it with a MikroTik RouterBoard AP which worked perfectly; but that led me to trying to nail down why my EVO was complaining about improper mail settings while I was at the office with an IPv6 address.

While I was researching this I noticed identical errors from two Verizon LTE users in the logs, and that’s when I ended up doing a debug trace on the SMTP session to discover the improperly formed IPv6 address literal from the Android Mail app.

After this it’s worked perfectly ever since.


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