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Signature guide

How to add a marketing banner to your email signature

A signature banner is the cheapest ad slot your company owns. Every reply, every intro, every quote — a wide image with one clear message and one link. Here's how to do it so it renders crisply in Gmail and Outlook, tracks clicks, and is actually swappable when the campaign changes.

Live example

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

Preview
ToMarcus Chen
SubjectQ4 launch — free trial
Thanks, Jonas
Jonas Berg
Sales Director · Wren
Wren
Ejonas@flywithwren.com
T+46 70 555 0143
Wflywithwren.com

Step-by-step

  1. 1

    Design the banner at the right size

    Use 600 × 200 pixels at 2× density (so export 1200 × 400) — that's the exact frame Gmail and Outlook give a signature banner. Keep the file under 200KB — larger and Gmail starts to clip your signature. Save as PNG for logos and flat designs, JPG for photos. One clear message, one call to action, generous padding around the edges.
  2. 2

    Host the image on a public HTTPS URL

    This is the single most-broken step. The banner needs a public https:// URL that Gmail's image proxy can fetch anonymously. Dropbox share links, Google Drive links, and files on your intranet all fail — Gmail's proxy gets a login page and the recipient sees a broken image. Use an image CDN, your marketing site, or a signature tool (Wren hosts every banner for you).
  3. 3

    Wrap the image in a click-tracking link

    An untracked banner is a wasted banner. Wrap the <img> in an <a href> that routes through a tracker before landing on your page — either a UTM'd link (?utm_source=signature&utm_campaign=q4) or a redirect that logs the click. You want to know how many people actually clicked, not just that you shipped it.
  4. 4

    Paste the HTML into your signature

    Add the banner block to the bottom of your existing signature HTML, then re-paste the whole thing into Gmail or Outlook settings. Do not use "Insert image" and upload the file directly — Gmail stores it as an attachment on every send, blowing up email size. It has to be an <img src="https://…">pointing at your hosted URL.
  5. 5

    Test in Gmail, Outlook, and Apple Mail

    Send a real email to a Gmail account, an Outlook.com account, and yourself on iPhone. Check three things: banner renders (no broken image icon), link works (goes where you expect with UTMs intact), size is right (not squashed to 400px wide, not clipped on mobile).
  6. 6

    Swap the banner without re-installing

    This is where DIY breaks down. If the banner URL is hardcoded to a specific file (q4-launch.png), every campaign change means every teammate re-pastes their signature. The fix: point the URL at a redirecting endpoint that serves whichever banner is currently live. Rebuild yourself, or use a signature platform where the banner URL is stable and the image behind it changes centrally.

Common questions

›The banner shows as a broken image or a red X in the recipient's inbox.
99% of the time this is a hosting problem: the image URL isn't publicly accessible over https. Open the URL in an incognito window — if you get a login page or a 404, that's why. Move the image to a public host (image CDN, marketing site, signature tool) and it will render.
›Should the banner animate (GIF or video)?
Only GIFs, and only on the first frame — Outlook renders just the first frame of any animated GIF, so design your key message there. Video does not render inline in email at all. Static images convert as well as animated ones in our data; keep it simple.
›How do I know if anyone actually clicks it?
You need click tracking on the outgoing link — either UTMs surfaced in Google Analytics, or a redirect service that logs hits. Email opens can't be tracked in signatures reliably (Gmail proxies pixels through a Google cache) but clicks can. Wren counts clicks per teammate and per campaign automatically.
›Can each teammate run a different banner?
Technically yes — the banner is part of each signature's HTML. In practice, running one banner across the whole company is what turns signatures into a real marketing channel. Fifty teammates running the same launch banner outperforms fifty different banners every time.
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