What improvements would you like to see with the Windows 10 mail app?

Similar to your number 1

I would like to see a reduction in size of fonts and UI as everything is so big (but this is how apps are so i doubt anything will change)

Nothing to me everything is as it should be.
Been using it since day 1 and what I do like is you can link all your inboxes together.

As you said, they need to add the ability to permanently change the default font used for the body of emails.

Also:

- Re-adding the 'Newsletters' folder. However this is due to be re-introduced with the new 'Clutter' feature, once the new Outlook backend is rolled out to everyone.

- Ability to change the order of email folders by dragging and dropping. As it is, the order is determined by the order you add them as favourites (or 'Sync This Folder' on Windows Phone). Currently, to change the order, you need to un-favourite them all, then add them to favourites in the order you want them in. Tedious.

- As a follow on from the previous point, when the Mail & Calendar apps are updated, Microsoft need to stop resetting which folders users have already added to their favourites and also stop re-ordering the users folders back to default. Keep users folders as they set them.

- There needs to be a way to clear the email address autocomplete list and/or delete entries from the autocomplete list. If a contact changes their email address, their old email address is still listed in the autocomplete list, therefore emails can accidently get sent to wrong email address. Also, the autocomplete list needs to update itself dynamically so that if an entry in the autocomplete list is one of the contacts in the People app, when you update their email address in the People app, the autocomplete field should also be updated.

- The 'Add New Folder' needs to be more prominent, such as adding it to the right-click context menu. As it is, it's hidden at the top of the 'More' menu where users just won't find it.

- If you're typing in a foreign language, spell check works correctly for that language. However, if you paste text in the same foreign language that you're typing in, spell check goes back to spell-checking in English and highlights it all as incorrectly spelt (even though you have your language set to that language in the Task Bar). This means you need to highlight the text you just pasted and go to Options and change the language manually, but it should do it automatically if you have that language set in the Task Bar.

- If someone for whatever reason embeds a picture in the email body, instead of attaching it, there needs to be a way to save that picture. The last one I recieved was a high resolution photo embedded in the email body and the only way to save it was to go to the web interface on outlook.com and use the browsers ability to right-click > Save picture as.

- Notifications need fixing badly. Quite often I open the Mail app to find new emails sat in my inbox, however there was no notification that they had arrived and no notifications in the notification centre to say they were there.

- Syncing needs fixing. Quite often emails I have deleted in the desktop Mail app, will re-appear on my phone the next time it connects to the internet, meaning they need to be deleted a second time on the phone.


Edit: Forgot to add.

- 'Deleted Items' doesn't need the 'Items' part in the name. None of the other folders such as Draft, Sent or Junk do.

- If you delete a folder, it doesn't appear in the 'Deleted Items' folder like it does in the web interface. You can only see it by going to 'More' and then deleting it from there, which isn't particularly user friendly.

- Also, if you're in the 'More' view and you accidently drag a folder into 'Sent' items for example, it's not possible to drag it back to the top level again. All you get is a 'no-entry' sign. You can only drag it to another folder, such as 'Inbox' for example.

- Come to think of it, what's the point of the 'More' section anyway? Just show all folders in the main interface and get rid of it entirely. I've never liked this menu, either for my own use or when explaining to other people how it works (which you need to do often, due to Microsoft keep resetting their folders when they issue a Mail app update).