replace usage of each() with foreach() for smtp

Summary:
this replaces uses with warning suppression of each() (depreccated in
PHP7, removed in PHP8) with foreach

Test Plan: can verify that these chages do work (tested on my own install)

Reviewers: O1 Blessed Committers, #blessed_committers, dsadad, avivey, valerio.bozzolan

Reviewed By: O1 Blessed Committers, #blessed_committers, dsadad, avivey, valerio.bozzolan

Subscribers: avivey, Cigaryno, speck, tobiaswiese, valerio.bozzolan, Matthew

Differential Revision: https://we.phorge.it/D25059