About a year ago, I began programming a small email reminder service in the spirit of followupthen or nudgemail. I felt that what they did should be rather easy to replicate (I was wrong, but it was still not too difficult) and I didn’t want to have my data on their servers anymore and wanted to be less dependent in general.
I had a running version after a couple of weeks of rare coding and stopped using my followupthen account for a while. The script broke down on me in the middle of the year because I had overlooked some parsing corner cases. In addition, I changed my webhost and so I was back with the commercial offerings for a while. In November, I finally found time to bring the project back in shape.
I have been using it actively over the past couple of weeks and I invite you to try it as well. The bitbucket repository with details is here: https://bitbucket.org/matthias_kauer/pybumper
Let me know how it works for you!
PS: If anyone is interested, I might also add a small number of users to my setup.