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Signature guide

Exchange email signature — the four ways it can actually work

Exchange (both the on-prem Server flavour and Exchange Online) offers more signature paths than any other mail platform — and it's easy to end up with two of them fighting each other. Here's a plain-English map of what's available, where each option renders in the email, and which one to pick for your team's shape.

Live example

One of ten built-in Looks. Every element is editable in the builder — colors, photo, links, tagline.

Preview
ToLegal team
SubjectContract review
Thanks, Jonas
Jonas Berg
Sales Director · Wren
Wren
Ejonas@flywithwren.com
T+46 70 555 0143
Wflywithwren.com

Step-by-step

  1. 1

    Path 1 — Per-user Outlook signature (the default)

    Every mailbox owner sets their own signature in Outlook. Full HTML, positioned directly under the message body. No central control. This is what your team probably already has — and why every signature looks slightly different.
  2. 2

    Path 2 — Exchange transport rule (free, server-side)

    Exchange Admin Center → Mail flow → Rules → Apply disclaimer to messages. You write an HTML block (or plain text) and Exchange stamps it on every outbound message. Central and free.

    The catch nobody mentions: Exchange only supports a limited HTML subset (no CSS classes, no external images unless inlined via CID) and it appends the disclaimer at the bottom of the message body — so on any reply chain your "signature" sits below every quoted message from the previous day. Fine for a legal disclaimer, terrible for a branded signature.
  3. 3

    Path 3 — Roaming signatures (new Outlook + Exchange Online)

    Microsoft rolled this out in 2023. Signatures are now stored on the mailbox itself in Exchange Online, so a user's signature follows them to any Outlook (Windows, Mac, web, mobile). Set once in new Outlook → Settings → Accounts → Signatures. Not central (each user still owns their own), but at least no more "my signature disappeared after I got a new laptop".
  4. 4

    Path 4 — Third-party server-side injection

    CodeTwo, Exclaimer, and similar tools route your Exchange Online mail through their service and inject the signature at send time. Full HTML, positioned correctly under the sender's message, per-department rules keyed to Entra ID / Azure AD. Per-mailbox billing, multi-day IT setup, and your mail routes through the vendor. Right answer at 500+ mailboxes; overkill at 30.
  5. 5

    What to actually pick

    • Under 100 mailboxes and you want a real branded signature: Wren. Each teammate installs from a personal link, owner controls design and banner centrally, flat $99/mo up to 50.
    • You only need a legal disclaimer stamped on outbound mail: Free Exchange transport rule.
    • 500+ mailboxes with compliance requirements: CodeTwo or Exclaimer. Genuinely worth the setup.
    • You just want your signature to follow you: New Outlook roaming signatures. Free, built in.

Common questions

›Can I have both a per-user signature and a transport rule disclaimer at the same time?
Yes — that's a common setup. The user's Outlook signature renders under their message body; the transport rule appends a legal disclaimer at the very bottom of the outbound message. Different jobs, different positions in the email.
›Why do images in my Exchange transport-rule disclaimer show as broken?
Exchange transport rules only reliably support inline CID-attached images or images at a public HTTPS URL. If your image is on an internal SharePoint / intranet URL, Exchange sends the reference but recipients outside the tenant can't fetch it. Host on a public CDN, or on a signature service that hosts assets for you.
›Do roaming signatures work in classic Outlook?
Only new Outlook and OWA fully support them. Classic Outlook still reads from the local %AppData%\Microsoft\Signatures folder. If half your team is on classic and half on new, roaming won't unify anything — you need a signature manager to actually converge.
›Will an Exchange transport rule catch mobile-sent mail?
Yes — that's its biggest genuine advantage. Because it fires at the mail server, mail sent from any client (mobile Outlook, iPhone Mail via ActiveSync, third-party clients) all get the disclaimer stamped on. Per-user Outlook signatures don't apply to any of those.
›Is Exchange transport rule enough for GDPR-style legal disclaimers?
For appending 'This email is confidential and intended only for…' style disclaimers, yes. It's the standard mechanism. For anything that has to render as a designed signature block with logo and photo, no — the HTML support is too limited and the position at the bottom of the reply chain undermines the whole thing.
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