Samsung S6 and S7, Maildroid app. Classical old POP3 setup. The POP server is under my control and definitely doesn't send out any notifications. It all works great. However I have found the following: On Samsung S6, droid v5, if the app is not running (e.g. left button / Close All) then it does not poll the POP box. If the app is running, it polls it at some indeterminate interval, around 1-3 minutes. No evident config for this. On Samsung S7, droid v6, regardless of whether the app is or is not running it (or "something") polls the POP box, as above. There is no config I can find anywhere for this. Not in the app and not in phone Settings. The S7 Maildroid config was copied from the S6 config using the feature the app provides for config backup/restore. I would prefer the S6 behaviour. What is surprising is that I have a PC based email client installed on about 4 other machines and if one of these is in the POP box, the others can't get in. The POP box is locked. This is as expected and is OK for my usage because I am the only user. But somehow the S6 and S7 (Maildroid) manages to get into the POP box and retrieve emails without ever upsetting the PC based client (which, running at my office, checks the POP box every 1 minute)! I would speculate that it merely silently fails to report the "lock" error message. But it also manages to retrieve big (multi MB) emails, without upsetting the PC client. No idea how that works... is it even possible to retrieve from a POP box without locking it? I do have Maildroid configured to leave messages on the server, so in principle this may be possible. But the biggest mystery is why the phone checks the POP box every minute or three, even when Maildroid is not running (on the S7) and why there is no config for this. Surely Android doesn't contain OS support for polling a POP box and sending notifications to the email client app, and starting it if following the notification (I have a beep and LED configured, in the app) the user launches the app to see the email. I wrote to Maildroid but they never replied.