If you have thought about how many words your subject line should be, here is some information I dug out from my archive of articles from “Marketo.”
After exhaustive testing and research, Marketo, a leader in email marketing determined the ideal number of words to have in your subject line in order to get the most clicks to open rate. That magic number is “7 WORD SUBJECT LINES.
However, if you are only interested in getting the highest open rate, than 4 WORD SUBJECT LINES work better
See The Chart Below.