Your biggest concern is how to gain new donors and re-engage lapsed ones, right? Opt-in would really be the best practice for all your marketing practices in the long term and Marketing Town is essentially the solution to their problem. With Marketing Town, you can get access to a business network of more than 900 compliant UK suppliers who openly inform individuals of the data points they are looking to collect and how their personal information is going to be used.
The changes to opt-in regulations might slow down your list growth in the short term, but it is not as hard you might think. After all, all you will be doing is marketing to individuals who are interested in hearing from you and thus improve your overall data quality. Non-profit organisations are required to go above and beyond the GDPR regulation when dealing with donors' personal information, so you need to take steps towards adopting an opt-in approach in your marketing communications.