Using php is it possible to send a jpg in the subject line of an email? I've noticed there are limited ways to send emolji
Not possible to add graphics like jpg, png or any other file format to the subject of a mail. Neither emojis.
The mail client can change some characters to emoji, for user friendly.
The mail client for example can change the <3 by a heart or :) by a smile face.
you cannot add it to the subject, just add this char and pray for the client change those chars.