Lumia 950 - WP 10 - Outlook Mail does not download e-mails automatically, why?

[Windows Central Question]

I received my Lumia 950 on friday and most things work like a charme, but Outlook Mails does not. I have four POP3 accounts I used to with the mail app of my old Lumia 1020 without any issues. Now Outlook Mail does not auto-download mails every 15 minutes as I told it to do in the settings (data use for LTE is activated). Rather it seems to check on e-mails at random (at least 30 or 40 minutes) and when new mails are found the tile and the lock screen only informs me on the mails on the last checkup (so if I had 10 new mails and on the next check there is 1 new, it only displays 1 new, instead of 11). Please tell me there is a way to fix this, because mail use is really important to me...Thanks in advance!