Vacation rental email campaigns getting terrible open rates, what am I doing wrong?

Started emailing my past guest list about 2 months ago. Built a decent sized list over the last couple years and figured I should use it.

Problem is my open rates are terrible. Barely anyone opens them and even fewer click through.

Using basic email software and just sending the same message to everyone about availability and discounts. Subject lines are pretty generic like "Book Your Next Stay" or "Special Offer for Past Guests."

Is this normal for vacation rental email campaigns or am I doing something wrong? What results are people actually seeing?

Starting to think maybe email just doesn't work as well as people claim or I'm missing something obvious.