This will be the post about HOW TO allow user's email change, only in phpBB OR WordPress.
This is a closed topic where will be added the easy procedure/steps to accomplish with this requirement, that is mandatory since 2.4.0>
A new option has been added:
that goes to replace the option "Link or not, the User ID1 in WP and user ID2 in phpBB".Password hash: WordPress or phpBB way
User ID1 in WP and user ID2 in phpBB, since 2.4.0, are NOT considered anymore: they are completely excluded to be linked by default (and will not be possible to link them).