What is your experience with using % in subjectline, eg. "Save 50%...". Will this potentially trigger spam-filters?
Any feedback appreciated.
I don't personally have any experience but my gut says that it would probably increase the overall spam score. Even if only by a few tenths of a point, since it is so common with spam it makes sense to me.
Perhaps someone has a definitive word on the matter?
I've found that sending a test email and then checking the message headers to be pretty useful.
From a recent message I received, the Spam Assassin headers look like this:
X-Spam-Score: 0.131 X-Spam-Level: X-Spam-Status: No, score=0.131 tagged_above=-999 required=999 tests=[HTML_50_60=0.13, HTML_MESSAGE=0.001]
A quick search for the rules (e.g. HTML_50_60) can be illuminating.
Alternatively, you could split you list 50/50 an monitor the results with a discount in the subject line and one without. More than often you'll find that each ISP will have their own spam-filters in place so it's hard to say.
Thanks for all your input!
An A/B split test could be a good solution (as in most cases when in doubt...).
Btw - really excited about this feature coming to Campaign Monitor!