Where signatures live
Classic Outlook on Windows
Signatures are files in the user's profile, three per signature: an HTML version, a rich text version and a plain text version, plus a folder of any images that were embedded rather than linked. The mapping between those files and the account is stored in the user's settings.
That explains most of the tickets:
- A new laptop means a new profile, and the files do not come with it.
- A repaired or recreated Outlook profile loses the association between account and signature.
- An embedded image lives in that folder, so copying only the HTML file gives you a signature with a broken image.
- A roaming profile that only partly roams gives you a signature that appears on one machine and not another.
Roaming signatures
Newer Outlook builds store the signature with the mailbox in the cloud instead of the computer. This is the behaviour you want: the signature follows the person. It is also why a signature can appear to change by itself. If a mailbox has a roaming signature and the machine has a local one, whichever wins depends on the build and the settings in force, and an update that switches the behaviour on can replace what somebody had locally.
The new Outlook, Outlook on the web and Mac
All of them read from the mailbox. A signature set centrally on the mailbox appears in each of them without anyone touching settings, which is the same mechanism that makes an old local signature look like it was overwritten.
The mobile apps
Outlook mobile keeps its own short signature, separate from all of the above. That is why someone with a correct desktop signature still sends a line about their phone from the train.
The three usual responses
- Send the HTML again. It works for that person, that day. It does nothing for the next new laptop.
- Script the files into the profile. It works on managed Windows machines, does badly on Mac, and does nothing for Outlook on the web or for phones. It also breaks quietly when a new Outlook build changes where things are kept.
- Put everything in a transport rule. Then the sender never sees their signature, and it lands under the quoted thread. The trade-offs are on the Exchange email signature management page.
Each of these treats the signature as a file on a computer. The reason the ticket keeps coming back is that the signature should be a property of the mailbox.
Manage the mailbox, not the machine
When signatures are written to the mailbox from a central template, the events that used to cause tickets stop mattering.
- A new laptop signs in, the mailbox has the signature, nothing is lost.
- An Outlook update changes storage behaviour, and the managed signature is still the one on the mailbox.
- A person changes department, and the next rollout gives them their new group's template.
- The mobile variant is deployed too, so the phone stops signing for them.
- If a rollout is wrong, rollback returns the group to the previous version in one click.
Nothing is installed on the endpoint and no script runs at login. The tenant connection, the template and the group rollout are described on the Outlook signature manager page and step by step on the how it works page.