wren.
Log inStart free
Signature guide

Office 365 email signature — the real 2026 guide

Microsoft has quietly reorganised how signatures work in Office 365 three times in the last two years. New Outlook stores them roaming with the mailbox; classic Outlook keeps them in %AppData%; OWA has its own separate copy that most people forget exists. Here's how to set one up correctly on each surface — and, if you're doing it for a 30-person team, when a signature manager is the honest answer.

Live example

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

Preview
ToJamie Cohen
SubjectQ1 review — proposal attached
Thanks, Maya
Maya Chen
Customer Success Lead · Wren
Wren
Emaya@flywithwren.com
T+1 415 555 0188
Wflywithwren.com

Step-by-step

  1. 1

    Decide which Outlook the team actually uses

    Office 365 ships three different Outlook apps under one name. The signature settings live in different places on each:
    • New Outlook (Windows) — Settings → Accounts → Signatures. Roams with the mailbox.
    • Classic Outlook (Windows) — File → Options → Mail → Signatures. Stored locally in %AppData%\Microsoft\Signatures.
    • Outlook on the web (OWA) — Settings gear → Mail → Compose and reply. Separate from both of the above.
    A signature saved in classic Outlook does not show up in new Outlook or OWA unless you set it manually there too.
  2. 2

    Build the HTML somewhere real

    Outlook renders signatures with the Word HTML engine, which strips CSS classes, ignores flexbox, and adds mysterious extra spacing around <div> tags. Build in a tool that uses nested tables and inline styles (Wren's builder is free — no signup) so what you see is what actually renders. Pasting from Canva, Figma, or a Google Doc is the fastest way to a broken signature.
  3. 3

    Paste into each Outlook surface (in this order)

    New Outlook first. Settings → Accounts → Signatures → New → paste. Set it as default for new messages and replies/forwards. Save.

    Then OWA — same process at outlook.office.com. Yes, you have to do it twice even though it's the same mailbox — Microsoft has not unified this.

    Classic Outlook, if anyone still uses it — File → Options → Mail → Signatures. Paste and save. If the images disappear, someone set Outlook to "Send pictures as attachments" — turn that off.
  4. 4

    Handle mobile Outlook separately

    Outlook mobile does not sync signatures from the desktop app — a source of ongoing frustration. On iOS/Android: open Outlook → tap your avatar → Settings gear → Signature. Paste the plain-text version there. Images won't render on mobile Outlook via the signature setting, so use a text-only variant for phone-sent replies.
  5. 5

    If it's for a team, don't do this 30 times

    Doing steps 3–4 on 30 workstations is a bad use of a day. Options, in order of cost:
    • Wren — each teammate opens a personal link, clicks Copy, pastes once. Owner controls the design and banner centrally. Flat $99/mo up to 50 people. No admin console.
    • Exchange transport rule — a free built-in option that stamps a disclaimer server-side, but it appends the text at the very bottom of the mail (below all replies) and can't do rich HTML reliably.
    • CodeTwo / Exclaimer — enterprise-grade server-side injection via a Microsoft 365 connector. Full HTML, per-department rules, mobile-sent mail covered. Per-mailbox pricing and multi-day IT rollout.

Common questions

›Why does my signature look fine in the Outlook preview and broken when the recipient opens it?
Outlook's compose window uses one HTML renderer; the received message often gets re-processed by the recipient's client (Gmail re-parses, Apple Mail changes the font stack). Test by sending to a Gmail account and an iPhone before rolling out. If images collapse to 400px wide, add explicit width and height attributes on every <img>.
›Can I set one signature for the whole Microsoft 365 tenant from the admin center?
Not natively for the Outlook client — the closest built-in option is an Exchange Online transport rule, which stamps a text disclaimer at the very bottom of every outbound message. It's fine for legal disclaimers, useless for a branded signature that should sit under the reply. For a real central signature you need either Wren (client-installed, centrally designed) or CodeTwo / Exclaimer (server-side injected).
›How do I get my company logo into an Office 365 signature without it breaking?
Upload the image to a public HTTPS URL and reference it with <img src="https://…">. Do not use "Insert picture from file" in Outlook — that attaches the image to every outgoing message and Gmail flags it as an attachment. Wren hosts logos and photos for you on a stable URL so this is never a problem.
›Does an Office 365 signature also apply to Teams messages?
No. Teams messages use a separate short signature configured inside Teams itself. Signature managers (including Wren, Exclaimer, CodeTwo) all target Outlook and OWA, not Teams.
›New Outlook or classic Outlook — which should the team standardise on?
Microsoft is pushing everyone to new Outlook by 2026. Standardise there if you can — signature settings roam with the mailbox, so a fresh Windows install picks them up automatically. Classic Outlook still has some enterprise-only features (COM add-ins, offline PST) so IT-heavy shops may need to keep it around.
Also useful