Posted on 14 August 2026

Why Your Email Signature Logo Shows Up as an Attachment (and How to Fix It)

You spend time on a professional signature. The logo looks fine when you send a test to yourself. Then a client replies: “Got your logo as an attachment.” Or worse — they never mention it, and every email you send looks slightly unprofessional.

This is one of the most common email signature problems, especially in Outlook. It isn’t random. It’s how many mail apps treat images that are embedded in the signature instead of hosted and loaded from the web.

Here’s why it happens, how to spot it, and how to fix it properly.

What “logo as an attachment” actually means

When someone opens your email, they should see your logo inside the signature block — like a normal webpage image. Instead, some clients treat the image as a separate file and show:

• A paperclip / attachment icon on the message
• The logo listed in the attachments pane
• Sometimes a second copy of the image at the bottom of the email

Recipients may think you meant to send a file. On mobile, attachments are easy to miss or ignore. Either way, it distracts from your message.

Why it happens

Most DIY signatures paste a logo file straight into Outlook or Word, then Outlook “embeds” that image in the message. Embedded images travel with the email as MIME parts. Many clients (Outlook especially) surface those parts as attachments.

Common triggers:

• Pasting a logo from Word or a local file into the Outlook signature editor
• Copying a signature that was built with embedded images from another app
• Using “Insert → Pictures” instead of an image URL that loads remotely
• Some “free” generators that export HTML with base64 or cid: image references instead of normal https:// image links

If the image isn’t loaded from a public URL when the email is opened, you’re in attachment territory.

Quick checks

1. Send a test email to a Gmail address and an Outlook address (ideally someone else’s).
2. Look for a paperclip or an Attachments section.
3. Ask: does the logo still display if images are blocked? Embedded logos sometimes still “attach”; hosted logos simply show a broken-image placeholder until images are allowed — which is normal and expected.

If you see the paperclip every time, your signature is almost certainly embedding the file.

How to fix it: host the logo, don’t embed it

A professional HTML signature should reference images like a website does:

<img src="https://your-cdn.example.com/logo.png" width="120" height="40" alt="Company logo">

When the recipient opens the email, their client fetches that URL. The image is not packed into the message as a file, so it shouldn’t appear as an attachment.

That’s the core idea behind hosted email signatures.

What “good” hosted images look like

• Served over HTTPS
• Reasonable dimensions (see our size & dimensions guide)
• Stable URLs that don’t expire mid-campaign (or that renew while you’re subscribed)
• No tracking pixels dressed up as logos

Fix options compared

1. DIY hosting
Upload the logo to your website or a CDN, then hand-edit HTML so every <img> uses that URL. Works if you’re comfortable with HTML and Outlook’s quirks. Easy to break on the next edit.

2. Keep pasting into Outlook
Fast short-term. Almost guarantees the attachment problem returns.

3. Use a signature tool that hosts images for you
You design in the browser; the tool serves the logo and banner from a CDN. You install clean HTML once. This is what Mirosign is built for — design free in the browser, then install HTML that loads hosted images instead of embedding files.

How Mirosign avoids the paperclip

In Mirosign you upload a logo while designing. On export, the signature HTML points at a hosted image URL rather than packing the file into every outbound email. Recipients see the logo in the signature; they shouldn’t get a mystery attachment.

That also helps with:

• Smaller email size (better for deliverability — more in our anti-attachment guide)
• Updating a logo in one place without re-pasting into every mailbox
• Keeping layouts more consistent across Outlook, Gmail and Apple Mail

Design a signature with hosted logos in the free Mirosign designer →

No account required to try the designer. You only subscribe when you’re ready to install and keep hosted images working.

Still seeing attachments after switching?

• Old signature still installed — remove the previous Outlook signature and paste the new HTML cleanly. Mixed old + new is a common trap.
• Forwarded threads — some clients re-attach images when people reply-all through long chains. Test a new email, not a reply.
• Multiple signatures — check you’re not still using a personal “legacy” signature on one device.
• Install steps — follow the guide for your client on our install pages.

Bottom line

Logos show up as attachments because they were embedded in the message, not loaded from the web. Host the images, use proper HTML <img src="https://…"> links, and reinstall the signature. That’s the lasting fix — and it’s exactly what a hosted signature tool is for.

Try the free designer on Mirosign →