Push doesn't work

The push function does not work (the settings are all correct), nor does the manual collection of emails work.
The emails arrive at some point, but very often very delayed, sometimes minutes, sometimes hours.
What’s wrong with that?
Otherwise: I like the new design very much!

Without more details and maybe even logs it will be hard to help you. Device, Android and K-9 version are important infos, and logs never hurt.

Smartphone: Samsung A40
Android: 11
K-9 Version: 5.806
Logfile is not possible: ADB is not working, I get the answer:
“adb.exe: no devices/emulators found”
Although the smartphone is correctly connected, the device is not listed.
Tried several times.

Is your mail imap or pop?

It’s IMAP. I want to use push.

Have you confirmed that your mail hosting provider supports push, not all do. Who is your provider, someone in this forum may have experience with them.

Yes, my provider (GMX) offers push. I’ve already installed other email apps and tried to see if push works. It worked well, but other apps are missing some features that only K-9 offers. So I would like to continue working with K-9.

I have this issue too. FairEmail works on my phone.

Huawei Mate 20 Pro
Version 5.806

Hello, I have a similar problem. I have two email accounts with K9: one from Deutsche Telekom (magenta.de) and one from vodafone (arcor.de).
The funny thing is that Push works perfectly fine with the Telekom account, but not at all with arcor.
I also know why. If I name the push folders in the settings and go back to the menu, it automatically sets the push folders to 0 again!
But I think everything is set correctly.
Frequency of the email query 15 minutes. Main and sub folders for Push. Under Advanced: 10 folders for Push.
So, as I said, it sets itself to 0 push folders.
Does anyone have any ideas?

If Settings →[Account] → Fetching mail → Push folders is set back to None automatically, it means your provider doesn’t support Push (or the IMAP IDLE extension, to be more exact).