You built a signature, sent a test email, and the logo came through as an empty box with a tiny red cross. Or worse — it looked fine on your screen and broke on the client’s.
Image problems in email signatures almost always come down to one of nine causes. Here is how to identify which one you have, and how to fix it for good.
These are two different problems with two different fixes, and people waste hours confusing them.
Right-click the broken image in the received email and choose to open it in a new tab. If the image loads in your browser, the file is fine and the recipient’s email client is blocking it. If you get a 404 or an access error, the link itself is wrong.
Everything below assumes you have done this check first.
This is the single most common reason. You dragged a logo from your desktop into the signature editor, and the HTML now contains something like file:///C:/Users/you/Desktop/logo.png.
That path exists on exactly one machine in the world — yours. Everyone else gets a broken image.
Every image in an email signature must be uploaded somewhere publicly reachable and referenced by a full https:// address. Your website, a CDN, or a signature tool that hosts images for you.
Modern email clients treat insecure resources with suspicion. Gmail, Outlook on the web, and most mobile clients will silently drop an image served over plain http://.
Open the signature HTML, find every src= attribute, and make sure each one starts with https://. If your host does not support HTTPS, move the images.
Some hosts, CDNs and site security plugins block requests that arrive without a matching referrer — a feature designed to stop other sites stealing bandwidth. An email client sends no referrer, so the request is refused.
Symptoms are distinctive: the image loads perfectly when you paste the URL into a browser, but never loads inside an email.
Fix it by whitelisting the image directory in your hotlink protection rules, or by hosting signature images somewhere that expects to serve them cold.
Gmail does not load your image directly. It proxies it through googleusercontent.com and caches the result. If you replace a logo but keep the same filename, Gmail can keep serving the old version — or, if the file was briefly missing, keep serving the broken state.
The reliable workaround is to never reuse a filename. Upload logo-v2.png instead of overwriting logo.png, and update the signature to point at the new file.
If you copy a signature and paste it with Ctrl+Shift+V, or into a field that only accepts plain text, all the HTML is stripped. Images vanish, links become bare URLs, and formatting collapses.
Paste with plain Ctrl+V into an HTML-capable signature editor. In Outlook, check that the account is composing in HTML rather than Rich Text or Plain Text — a mismatch there causes a whole family of related problems, covered in our guide to signatures showing up as attachments in Outlook.
Outlook desktop in particular handles images poorly when dimensions are not declared. Depending on the recipient’s display scaling, the image can render at the wrong size, collapse to a sliver, or fail to reserve space at all.
Always set dimensions as HTML attributes on the tag itself, not only in CSS:
<img src="https://example.com/logo.png" width="180" height="60" alt="Company logo">
A three-megabyte photograph exported straight from a camera will time out on slow connections and may be dropped entirely by mobile clients.
Keep every image in a signature under about 100 KB, and the whole signature well under half a megabyte. See our email signature size guide for the specific numbers.
Many corporate mail systems and privacy-focused clients block remote images until the reader clicks “show images”. You cannot override this, and you should not try to.
What you can do is make sure the signature still works without images. Never put your name, job title, or phone number inside a picture. Give every image meaningful alt text so that a blocked logo reads as your company name rather than as nothing at all.
Signatures are set once and forgotten. Then the site gets rebuilt, the media library is reorganised, and every signature in the company quietly breaks — usually without anyone noticing for months.
If you manage signatures for a team, keep the images on a stable path that does not move when the marketing site changes, and check them after every redesign.
src is a full https:// addresswidth and height are set as attributesalt textMost of these failures come from hand-assembling HTML and hosting images wherever happened to be convenient. A signature built with the Mail Ink generator ships with images already hosted over HTTPS, dimensions declared, and alt text in place — so there is nothing left to break.