mrsmithjr :
Hello, maybe its a dumb question but I hope someone can answer. How is it so that you can use your outlook account to login into google services like youtube and gmail? As I understand it Microsoft and google are separate companies, so how does youtube check your outlook details when you login?
Pretty much all email services allow you to connect via POP or IMAP. POP is the older one, and is the protocol used to download your email from the service to your computer (this deletes it from the server, so the copy you downloaded is now the only copy in existence). IMAP is the newer one, and gives you the option to download your emails like POP, or to leave the emails on the server but access them remotely. Your email program then essentially becomes your email client, instead of the email server's website (Gmail or Yahoo mail).
Outlook supports both POP and IMAP. So you can use Outlook to access and manage your emails on Gmail or Yahoo. That is, you run Outlook to read, manage, and send emails, instead of the Gmail or Yahoo Mail website. But the emails (and your email address) are all handled by Gmail or Yahoo. Any other local mail program which supports POP or IMAP can do the same thing. Thunderbird is the popular open source one.
https://support.google.com/mail/answer/7126229?hl=en
https://support.office.com/en-us/article/import-gmail-to-outlook-20fdb8f2-fed8-4b14-baf0-bf04b9c44bf7
https://help.yahoo.com/kb/SLN4075.html
https://www.lifewire.com/access-free-yahoo-with-outlook-1173788