I can't speak for iOS, but with macOS and Outlook, I can select the top email and then Shift-click the bottom email. That selects all of them. Then, I click Delete. Pressing Command-A works (and that's the same as Edit > Select All, which does appear in the Edit menu).

Last edited by jchuzi; 05/18/18 02:07 PM.
Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365