HTML email campaigns being delivered as plain text
I'm new to the forum and was wondering if anybody could help with an email marketing issue i'm having.
In November my companies email open rate dropped from 21% to 5% and hasn't risen again since. After some research it looks like our database contacts are receiving the plain text version so the images aren't loading, which includes the image that records opens and sends it back to our ESP.
These contacts receive HTML emails from other companies and were receiving them from us up until November.
Does anyone know what could cause our emails to just suddenly start being delivered as plain text instead of HTML?
Thanks
"Opportunity is missed by most people because it is dressed in overalls and looks like work." Thomas Edison