Mail and Yosemite

Depends on the internet provider for the mail. AOL, Yahoo, Verizon and SBC have all made their email work best via IMAP, and not pre-installed settings on Mac OS X Mail. Check their webmail settings are ready to distribute via IMAP and then use IMAP settings on Mac OS X Mail. Microsoft uses Exchange servers for their Outlook and Hotmail email addresses.

You can upgrade to El Capitan for better compatibility with newer software, and if you aren't dependent on old versions of Microsoft Software all the way up to Mojave. Beyond that many software title compatibility for older software breaks across the board because you need 64 bit compatible applications. And at minimum you should be able to run Catalina once you have compatible applications.

Hello and welcome to Apple Support Communities, Svenno49.

If we understand your post correctly, you aren't able to send or receive email on your MacBook Air. We’d like to help.

Follow the steps in this article to troubleshoot your email account:

If you can’t send or receive email on your Mac

Let us know if that resolves this issue for you.

Thanks for using the Apple Support Communities.