From here:
http://forums.d2jsp.org/topic.php?t=73007316&f=34Quote (Yakir @ Jul 26 2015 07:50am)
Do the following
Diablo 2 -> Battle.net -> Account Settings -> Change Email
If that doesn't work, you can try from the battle.net site but other than that there is no other way.
This post was edited by Phyerox on Oct 17 2017 10:29am