Windows 10 Mail App limitations

Windows 10 comes with a new Mail and People applications which are optimised for use with Cloud services (Outlook dot com). The new applications bring significant reductiuons in functionality compared to the earlier versions of Outlook Express (XP), Live Mail Essentials (Vista, Win 7) and even the Mail app in Windows 8/8.1 despite the similar look and feel on the surface.

Folder Structures

1. There is no support for a local folder structure.
2. Simple Pop3 mailbox accounts do not support folders at all.  Some Cloud services (outlook dot com) may support folders over pop3 but this uses a proprietary (per provier) protocol.
3. IMAP folders are cached localy and synchronised when online. However, deleting the IMAP account removes the local (cached) copy of all messages.
4. IMAP folders can not be created from the Mail app. They must be created on the server in some other way and syncronised to the local cache copy.

Import and Export

1. There is no straightforward way to import mail messages from Mail Live Essentials or any other mail client. 
2. Messages downloaded by Pop3 must be re-uploaded to a suitable mailbox.  The Windows 10 Mail app will then download the messages when the account is added to Mail.
3. For any but a simple mailbox, it is recommended to use an IMAP service to transfer the foolder structure.  However, the Mail app may refuse to work with some versions of Dovecot.
4. IMAP folders may need to be created manuall on the server
5. IMAP folders will need to be synced manually per folder

Contacts and People

1. When addressing messages in the Mail app, the Contacts folder and the People app's database are searched for completion suggestion.
2. Contact files can be created in the Contacts folder of the user profile similar to Windows Vista / 7 but they are separate and not used by the People App.
3. The People app does not support import of contact data locally.  Similar to the Mail app, the People app only caches locally the data held by a Cloud address book service.
4. To migrate contacts to the People App the contact data must be exported and uploaded to a suitable Cloud Address bool service provider (Outlook dot com). 
5. Address book storage may be available from other Cloud and IMAP providers but the functionality is proprietary.
6. Contact information cached llocally by the People app is associated with an internet account and will be deleted from the local system when the account is removed.

Probably easiest to use Outlook dot com or consider Thunderbird if determined to avoid depending on access to the Cloud for .