Hi there, @Helmut. Not quite. I edited my post. Not totally sure, for I haven't performed this. I've had an MS account for many years and used their mail clients, so I've had no need to.
The People app is a modern Store app with no way to import .csv files. I'm thinking the Windows Live Mail (Icon) is a portal to upload a .csv file into one's MS account.
Sorry for the late response. Thank you so much for the tip, It worked but unfortunately there is still a problem. I now have all my contacts in People folder; however, only the initial contacts that came from my yahoo account appear when I fill in the "To:" field on a new email. In other words: One of my contacts that I had in Thunderbird was "Carole" and when I wish to send Carole an email I type "C" (now all the contacts under "C" should show up as options, but "Carole", who has been imported from Thunderbird to Windows 10 Mail, does not show up). Very weird. Also when I click the little people icon with the plus sign at the right side of the "To:" field in a new email, Carole is not listed there either. Please see image to hopefully clarify what I mean.
Oh for cry eye! Don't you just love tech?!! Sheesh!Sorry for the late response. Thank you so much for the tip, It worked but unfortunately there is still a problem. I now have all my contacts in People folder; however, only the initial contacts that came from my yahoo account appear when I fill in the "To:" field on a new email. In other words: One of my contacts that I had in Thunderbird was "Carole" and when I wish to send Carole an email I type "C" (now all the contacts under "C" should show up as options, but "Carole", who has been imported from Thunderbird to Windows 10 Mail, does not show up). Very weird. Also when I click the little people icon with the plus sign at the right side of the "To:" field in a new email, Carole is not listed there either. Please see image to hopefully clarify what I mean.
I'm in my Insider partition and the People app link is broke. Let me reboot to my W10 CU where I can get at People. Be right back.
Ok. All the contacts show in the left column, correct?
When you click on a contact does all there info you have on them show in the right pane?
In the People app I mean.
Go into the People App Settings > Filter Contacts List, and make sure you have the right Accounts listed, add/remove as required.
On mine
Hide Contacts without phone numbers is OFF.
Show contacts from, has these ticked
MS Account, Gmail, Outlook (Mail and Calendar)
People App is version 10.2.1451.0
Mail App is version 17.8218.40507.0
Along with the Mail App, these seem to be updated every week, sometimes irritatingly changing settings or adding a 'feature'.
Good morning, Razz. We'll try to get to a solution today I hope. To review > The Email app is not syncing the contacts imported from Tbird and Tbird contacts hyperlinks do not work in the People app.
It may be that the way we imported the Tbird contacts might not totally work. Hopefully that's not the case.
Let's check the settings Helmut just suggested. Also, there is a thing called "App connector" that allows apps to sync with one another. Open Settings app > Privacy > Go through the whole list and make your choices qualify the connections/app syncing with one another.
Make sure all your apps are up to date in the Store app. Store app > Click on your account logo > Downloads and updates. While you're there you may want to check the Store settings there.
If that doesn't work try: https://support.microsoft.com/en-us/...r-windows-apps
Hi Helmut. My People version and Mail version are the same as yours. My needed accounts are checked.
Just to make it clear: All my contacts are listed but except for my original contacts imported from Yahoo, any other desired contact does not appear as an option when I am trying to send an email to them. I type their name in the "To:" field and their name is not in the list of options.
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Correct, all my contacts are indeed listed, Yes the contact info shows, but sadly their email address is not hyperlinked so clicking on it does nothing. 
That would have been a work-around. I've included an image.
