I have connected Mail app with my Outlook account. The problem is that the email app doesn't show custom-made folders that I have created using the Outlook web version. I have archived mail into those folders but I'm not able to access them via app because they are not shown. If I go to settings, I'm only able to turn on syncing with folders like inbox, sent etc my custom folders are not shown.
@nerkla: The Email app acts as a hub of sorts for any Email accounts you want to add, but it may not mirror any personal settings you have applied to the accounts themselves. If you haven't done so already, please open the Email app > Tap the 3 lines in the top left > Tap the cog in the top right of the pop up window > Select your account > Email folders to sync, and explore your options here.
If the folders aren't available then, in this instance, I recommend using the dedicated Outlook app. This may already be pre-installed on your device - swipe up from your Home Screen > Microsoft folder > Outlook - or it can be downloaded from the Google Play Store. I hope this helps.