Help Why is my POP3 email app constantly checking the POP mailbox?

[peterh337]

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.

 

[Slug]

is it even possible to retrieve from a POP box without locking it?

It shouldn't be; RFC1939 requires that an authorised client be given exclusive access to the maildrop, as specified in Section 4.

Once the POP3 server has determined through the use of any authentication command that the client should be given access to the appropriate maildrop, the POP3 server then acquires an exclusive-access lock on the maildrop, as necessary to prevent messages from being modified or removed before the session enters the UPDATE state.

I do have Maildroid configured to leave messages on the server, so in principle this may be possible.

That only ensures that no messages are deleted from the server when the session enters the UPDATE state i.e. when the client sends a QUIT command.

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.

The first thing to check is that the polling intervals set in the email clients on each device are the same. I suspect that "closing" an email client will merely result in it restarting immediately unless polling is disabled completely. If it's configured to poll for mail every x minutes then it's going to restart to follow that instruction.

 

[peterh337]

Maildroid has no polling config at all.

The fact that it does it when the app is not running suggests that it loads up some sort of background task. Where could I look for that?

Also on the S6 it did not poll unless the app was in the list of apps (left button).

I don't really want to dump this app because for various reasons I use POP3 and very few apps support that, and offer an option to delete from server which I find very handy when away from home, to remove unwanted emails.

 

[lunatic59]

Maildroid has no polling config at all.

Open Maildroid, go to settings>connection management>default>connection management and you should see where to change the polling frequency.

 

[peterh337]

Thank you!
I would have never found that...

The curious thing is how the S7 config ended up so different from the S6 config, given that the S7 config was imported from the S6, via Maildroid's config transfer feature.

 

[lunatic59]

Could be the s6 was Lollipop and the s7 is Marshmallow ... or evil sprits. Your guess is as good as mine.

 

[peterh337]

More likely, Maildroid intentionally doesn't transfer that part of the config, in order to restore the defaults which they think more people will prefer, and they probably know almost nobody is going to find that config menu