How do I add an email signature in Outlook, and can I make it auto-add to every email?

In new Outlook and the web: Settings (gear) > Accounts > Signatures > create one, give it a name, type and format it, then set the dropdowns for 'New messages' and 'Replies/forwards' to that signature so it auto-adds. In classic desktop Outlook it's File > Options > Mail > Signatures. You can have multiple signatures (say a full one for new emails and a short one for replies) and pick a default for each. Add a logo or link with the little image/link icons in the editor. One gotcha: web and desktop Outlook don't always sync signatures, so you may need to set it in each.

Set the 'New messages' and 'Replies/forwards' dropdowns to your signature, that's the auto-add part people miss. Otherwise you've made a signature but still have to insert it by hand every time.

Make two: a full signature for brand-new emails and a stripped-down one (just your name) for replies, so you're not repeating your whole block down a long thread.

Heads up that web Outlook and desktop Outlook keep separate signatures and don't reliably sync, so if you switch between them, set it up in both places.