Stopped recieving mail

[stphn]

Does it maybe change when you change your network, i.e. switching from Wifi to mobile data or vice versa?

Then it maybe could be related to

K-9 5.6.00 not notifing me

I remember that on my son’s Samsung S7 he also experienced something similar: it worked for some time and then stopped. Once changing the network it worked again for some time. If I recall correctly then it had been solved by disabling all kind of optimizations - Samsung is known to do aggresive optimizations on apps.