Depending on the person, amount of email they do on their phone can be an outrages amount id say some people I know do at least 65-70% of their emailing on their phone, especially if it is their own personal email and not their work email.
So this is definitely something my PAR Clients and you may want to take into consideration. Perhaps making sure you include a phone number on each of your emails that way they can relate back to the email and simply click on the phone number to make a call. This sort of gives them that quick “call to action” right there on the phone, obviously works well if you have a delivery services of some sort.
You may even consider making your templates more “mobile friendly” you can do this by making sure your email looks good even without images by using colors and adjusting the fonts.
For a lot of people’s email addresses you have to “ok” that it is ok for that email to show images. I know from my personal experience I scan through the email first to see if it worth a damn before I even ok it.
Point being it that you need to make sure that your email looks fine without the images, that way when I am doing my quick scan it is still appealing to the eye and I can get this jist of it by looking at bolded text. This is one technique that I always use in my blog.