Outlook mobile signatures: why they vanish and how to get them back

It is one of the most visible and least addressed gaps: the carefully deployed desktop signature disappears the moment the employee replies from their phone. In its place, a “Sent from Outlook for iOS”, or nothing at all. On sales conversations, the effect is immediate.

Why the desktop signature does not follow

The cause is structural. A signature created in Outlook for Windows or Mac is a local artefact: it lives in the user’s profile on that computer, as HTML and RTF files alongside an images folder. Nothing in that mechanism is designed to travel back up to the service.

The Outlook mobile app, for its part, manages a signature field of its own, stored in the app’s settings and pre-filled with generic text. The two systems ignore each other.

The result is that one person effectively has two different signatures, one of which they never chose. And because nobody rereads their own messages sent from the phone, the gap goes unnoticed for months.

The real scale of the problem

It is tempting to treat mobile as marginal. That has not been true for a long time: a substantial share of business replies — while travelling, between meetings, in the evening — leave from a phone. Those are often the most responsive exchanges, and therefore the most commercially sensitive.

Put another way, the signature is missing precisely where it would be most useful: on quick replies to people who do not know you yet.

The patches, and why they hold badly

Asking everyone to configure their mobile signature. The most widespread and least durable solution. The mobile field does not accept rich HTML: pasting a template produces a degraded result, without the logo, with random line breaks. And every employee produces their own variant.

Sending instructions with text to copy. Same problem, plus the usual attrition: three months later, half the estate has not done it, and new joiners never received the instructions.

Going through an Exchange transport rule. It covers mobile well, since it acts server-side — but it brings its own limits: the sender never sees their signature, threads stack blocks, and encrypted messages escape it. The detail is in add-in or transport rule.

The only approach that gives the same result everywhere

For the signature to be identical on desktop and mobile, it must depend neither on the machine nor on the app, but on the service. That is the principle of the add-in: it runs inside Outlook — including Outlook mobile on iOS and Android — and inserts the block while the message is written, with directory data and the current campaign banner.

It is the same mechanism that settles desktop deployment, described in how to deploy an Outlook signature: mobile then stops being a special case and becomes one more client.

The employee has nothing to configure, on any of their devices. If they change phone, the signature follows. If their job title changes in the directory, it updates everywhere at once. The environments covered are listed on the Microsoft 365 add-in page.

Worth knowing: remember to remove the old local signature from the mobile app at deployment. Otherwise the two stack up, and the message ends with the company signature followed by “Sent from Outlook for iOS”.

Designing a template that survives a phone screen

A signature designed for a 1,400 px wide screen fares badly at 390 px. Three precautions cover the majority of cases.

Limit the width. A block of 500 to 600 px maximum, that shrinks cleanly. Beyond that, the mobile client forces horizontal scrolling or shrinks everything until it is unreadable.

Avoid tight multi-column layouts. A logo on the left and a block of contact details on the right works; three columns do not.

Test for real. The multi-client preview in the Signally editor includes mobile rendering, but nothing replaces a real send to your own phone before going wide.