The first thing to do is not panic. The figures suggest that just 3% of the adult population is vegan. However, the numbers are increasing, and you should monitor how they change.
Tesco’s own brand of vegan foods, rather oddly named Wicked Kitchen, has been going for over a year. It proudly states on its website that it won an award. If they think the demands of veganism are worth covering, then it tends to indicate that it is something email marketing should concern itself with.
It is not all the preserve of groceries though. Many of the items you sell might have animal products in them, or use such material in their manufacture. Chocolate is, obviously, unsuitable for vegans, so your Easter images might have been a poor choice. Less well known is that Worcestershire sauce contains anchovies. Anything fortified with vitamin D3 probably has lanolin in it. Beer, wine and ciders may not be suitable for vegans, although there are vegan alternatives.
What could be wrong with an image of people drinking coffee? With a bit of care, it could be nothing as there are many milk substitutes which look that same, although beware the chocolate dusting on cappuccinos.
The rate of take-up of veganism is not uniform across the age range. The majority are millennials. If your products are aimed mainly, or even substantially, at this demographic then there are certain steps that you might usefully take.
1/ Ask those on your email marketing lists if they are vegans or vegetarians. The norm is that they will be only too willing to identify as such.
2/ Ensure images in an email marketing campaign are unlikely to affront them. At Christmas it might be best if you did not show a turkey being carved.
3/ The copy should be vetted for similar reasons.
Once you know which on your email marketing lists are vegans, treat them accordingly. It is not all negative of course. If certain of your products are suitable for vegans, such as wine without the use of isinglass, then boast about it. You could be targeting a growing section of society.