Key takeaways
- Most problems come from images that aren't hosted at a public https:// address.
- Classic Outlook blocks external images by default until the reader allows them.
- Always include alt text so the signature still makes sense when images are blocked.
In this article
- 1. The image isn't hosted online
- 2. The recipient's email app blocks images
- 3. Images arrive as attachments
- 4. The image address uses http:// instead of https://
- 5. The image was moved or deleted
- 6. The file type isn't supported
- 7. The image is too large
- Outlook-specific quirks worth knowing
- A two-minute test before you roll it out
You spent time getting your signature just right. Then a client replies, quoting your email, and where your logo should be there's an empty box, a red X or a paperclip.
It's one of the most common email frustrations, and the good news is that it nearly always comes down to one of seven causes. Work through them in order; most people find theirs in the first three.
1. The image isn't hosted online
This is the big one. When you paste an image from your computer into a signature, many apps either embed it in each email or link to a file on your own computer. Neither works reliably for the person receiving the email.
How to fix it: Make sure every image in your signature points to a public https:// web address. A quick test: right-click the image in your signature settings, copy the image address, and open it in a private browser window. If it loads, it's hosted. If not, that's your culprit.
2. The recipient's email app blocks images
Some email apps don't load images from the internet until the reader says so. Classic Outlook for Windows does this by default, unless you're in the reader's safe senders list. Your signature isn't broken; it's waiting for permission.
How to fix it: You can't change the reader's settings, but you can make sure your signature still works without images. Keep your name, title and phone number as real text, and give every image alt text (for example "Northwind Studio logo"), which shows in place of the image.
3. Images arrive as attachments
If people tell you every email from you has attachments named image001.png, your images are being embedded rather than linked. Outlook does this most often when images are inserted directly from your computer into its signature editor.
How to fix it: Rebuild the signature with hosted images. In the SignaturesDB editor, images are uploaded to a public address before you copy, and the editor warns you if one isn't hosted yet.
4. The image address uses http:// instead of https://
Many email apps refuse to load images over insecure http:// connections, or show a security warning. Gmail routes images through its own secure proxy, which can fail with some insecure addresses.
How to fix it: Check that every image address starts with https://. Most hosting services and website builders support it at no cost.
5. The image was moved or deleted
If your signature points to an image on your website, and someone redesigns the site, the old address can quietly stop working. Every email you've ever sent loses its logo on the same day.
How to fix it: Keep signature images in a dedicated, stable location that nobody will tidy away, and avoid addresses that look temporary or contain long tracking codes.
6. The file type isn't supported
SVG images don't show in Gmail and many versions of Outlook, and WebP support is still patchy. An image that looks perfect on your website can be invisible in email.
How to fix it: Use PNG for logos and icons and JPG for photos. Our email signature size guide covers formats and dimensions in detail.
7. The image is too large
Very large images can be resized unpredictably, slow to load, or clipped. Some apps also cap the total signature size; Gmail, for example, allows up to 10,000 characters per signature.
How to fix it: Save images at twice their display size, no larger, and keep each under about 100 KB.
Outlook-specific quirks worth knowing
Classic Outlook for Windows uses a different rendering engine from most email apps, which explains a few things you might notice:
- Rounded corners show as square, including round headshots.
- Images can appear larger if their width and height aren't set in the HTML.
- Extra spacing can appear between lines or table rows.
- Older versions show only the first frame of an animated GIF.
None of these break your signature, but they're good reasons to keep the design simple. Our Outlook installation guide walks through the setup for each version.
A two-minute test before you roll it out
- Send an email with your new signature to a Gmail address and an Outlook address.
- Open both on a computer and on a phone.
- Check with images blocked: does the signature still tell people who you are?
- Reply to the email and check the signature in the thread.
If all four look right, you're done, and you won't be getting those "your logo is broken" replies again.
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Frequently asked questions
Why are the images in my email signature not showing?
The most common reason is that the images aren't hosted at a public https:// address. Other causes include the recipient's app blocking images, unsupported formats such as SVG, and images that were moved or deleted.
Why do my signature images show as attachments?
They're being embedded in each email instead of linked from the web. Rebuild the signature with images hosted at a public https:// address.
Why doesn't Outlook show my signature images?
Classic Outlook for Windows blocks external images by default until the reader allows them or adds you to their safe senders. Use alt text so your signature still makes sense.
