How Do Contact folders fit into POP & MAPI accounts in Office Outlook 365

How Contacts fit into POP & MAPI accounts in Office Outlook 365?

Discussion-

I use two accounts in my Outlook 365: POP and MAPI. Years of migrating from one PC to another, I now seem to have the problem that I can’t always find/search for the email address that I need.

There are two contacts folders – one in each account

Contacts Properties in each shows mailto:name1@domainname.com  and mailto:name2@outlook.com

Each has significantly difference number of contacts.  (properties show number of all items)

Problem- 

     has arisen that I can’t access all emails accounts in the mailto:name1@outlook.com account.

Questions-

      Can I must copy one contact folder into the other outlook.com account?

      Change the properties name?

      Can I copy the "suggested" from one account to the other that has very few suggested contacts?

      Where are these relationships described?

      Is the contact properties email supposed to match the particular account?