New signature is not working due to images

Question

We have recently been sent a new signature for our work emails - that contains attachments in. Others in the company are using them and it seems to be working fine.

However, when I copy and paste either from the original email we were sent to copy the new signature template from or from others who are using it and I try to construct a new message it comes up with - ''This draft is larger than the maximum allowed length and it can't be sent or saved correctly. To fix this, try moving embedded images to attachments''

Of course, there are no embedded images in the draft emails - but there are images with the signature. I am confused as to why this works fine for colleagues but on my email it does not. I have tried making the attachments smaller but still, the issue persists.

Answer 1

Dear Amber H, 

Thanks for using Microsoft products and posting in the Microsoft Q&A Forum. 

We understand how frustrating it must be when your new email signature, especially one used successfully by others in your company, is causing problems only on your end. 

Based on the error message you received - “This draft is larger than the maximum allowed length and it can’t be sent or saved correctly. To fix this, try moving embedded images to attachments.” - this typically occurs when the total size of an email, including hidden formatting, embedded image data, or MIME encoding, exceeds Outlook Web’s internal limits. 

Even if the signature appears clean, copying it from an email may introduce hidden metadata or base64-encoded image content that bloats the draft size. 

To help resolve this, please try the following steps: 

1. Avoid Copy-Paste from Emails 

Instead of copying the signature from a message body: 

• Ask your IT team or colleague for the raw HTML file or a .txt/.html version of the signature. 
• Import it directly into Outlook via: 
  Settings > Account > Signature 

This ensures the signature is added cleanly without hidden formatting. 

2. Check for Embedded Metadata 

Even if no images are visible in the draft, Outlook may have encoded them during copy-paste. 

• Use a plain text or HTML editor (e.g., Notepad++) to inspect the signature for base64 image strings. 
• If found, consider replacing them with externally hosted image links. 

3. Host Signature Images Externally 

Instead of embedding logos or banners: 

• Upload them to a secure host (e.g., your company’s website or SharePoint). 
• Reference them using HTML: https://yourdomain.com/logo.png 

This reduces the draft size and avoids triggering the error. 

4. Recreate the Signature from Scratch 

Clear any cached signature settings and manually rebuild the signature in Outlook Web: 

• Go to Settings > Account > Signature 
• Remove the current signature 
• Restart the browser and re-add the signature using clean HTML or plain text 

Final Tip:

If others are using the same signature without issue, consider: 

• Differences in Outlook version or platform (Web vs Desktop) 
• Mailbox-specific limits or policies 
• Copying method introducing extra formatting 

Please let us know if these steps help. We look forward to your response and are here to assist further if needed. 

Best Regards, 

Victor Vu | Microsoft Q&A Support Specialist  

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