Outlook signatures have one genuinely confusing behaviour: there isn’t one signature, there are three. The desktop app, the web version and the phone app each keep their own – which is why yours “disappears” on a new machine, or why mail sent from your phone goes out without it.
Classic Outlook on Windows
- Go to File > Options > Mail and click Signatures
- Click New, name it, and build the signature in the editor
- At the top right, set it as the default for New messages and, if you want it on replies too, Replies/forwards
Recent versions sync desktop signatures to your account; on older setups the signature lives on that one PC, so a new machine means setting it again – or see the company-wide option below.
New Outlook and Outlook on the web
- Click the gear, then Mail > Compose and reply (or type signature into the settings search)
- Create the signature and pick the defaults for new messages and replies
These two share the same signature, so setting it once covers both.
Outlook mobile
Tap your profile picture, then the gear, then Signature. Out of the box it says “Get Outlook for iOS” or “Get Outlook for Android” – most people prefer their own name. Keep the mobile one short; nobody needs your full address block on a two-line reply from a train.
The tidy option: one signature for the whole company
If keeping signatures consistent across staff, devices and job-title changes is becoming a chore, we can apply a company signature centrally instead: same branding for everyone, details pulled from the directory so they’re always current, applied to every email from every device, and nothing for staff to set up or forget. Raise a ticket if you’d like that in place.