Blurry logo in Outlook signature? Fix size and compression

A blurry logo in an Outlook signature usually has one of two causes. The file is too small for the size it is shown at, or Outlook compresses inline pictures when you send. Export the logo at twice its display width, set that display size in the signature, and in classic Outlook for Windows turn off compression. The steps and the caveats are below.

Why Outlook makes a logo look soft

Office compresses pictures toward a target resolution. Microsoft says the default picture resolution in Microsoft 365 is 220 ppi. A picture larger than that target is scaled down. A picture smaller than the space it fills in the signature is stretched, and a stretched logo is the soft one.

Many older guides recommend 96 ppi, which was a different default in some older versions. Check the version you run before you copy a figure from a forum.

Step 1: Export the logo at twice its display size

1. Decide how wide the logo should appear. Our size guide suggests 100 to 160 pixels for a logo.
2. Export the file at double that width, so 200 to 320 pixels. The extra pixels keep the logo sharp on high-density screens.
3. Use PNG for a logo with flat colours, text or a transparent background. Use JPG only for photos.
4. Resize the file, not the picture inside the signature editor. Insert it at its final pixel size.

Step 2: Set the display size in the signature

After you insert the picture, set its width in the signature editor to the size you chose in Step 1, not to the size of the original file. Keep the height in proportion. If you paste signature HTML from a tool, check that the image has both a width and a height attribute.

Step 3: Turn off image compression in classic Outlook for Windows

1. Open classic Outlook for Windows. The option needs Outlook for Microsoft 365 version 2109 or later.
2. Go to File > Options > Mail.
3. Click Editor Options, then open the Advanced tab.
4. Under Image Size and Quality, tick Do not compress images in file.
5. Set Default resolution to High fidelity.
6. Click OK, then send a test message to yourself.

Troubleshooting: the logo is still soft

• You use new Outlook for Windows or Outlook on the web. The compression option above is not in new Outlook yet, so Step 1 is the only control you have. Test the signature in each app you send from, because each has its own editor.
• It looks sharp in your sent folder but soft to recipients. A reply or forward can soften the image again, and you cannot control that from your side. CodeTwo notes that quality is not guaranteed once the message is sent.
• Nothing changes after Step 3. Outlook may still be using the old picture. Delete the logo from the signature, insert the new file, and save the signature.
• You are not sure what size the file is. Check the pixel dimensions in the file's properties. The size shown in the editor is the display size, not the file's real size.

How Sendoff handles this

Sendoff writes explicit width and height attributes on every logo, so the size you pick is the size recipients see. Upload the file at twice the display width in the signature generator. If you want the term defined, the retina image entry explains why double-size files look sharper.

For the full Outlook set-up, see the Outlook integration guide.

Sources

• Microsoft Support, Reduce the file size of a picture in Microsoft Office (220 ppi default, Image Size and Quality): https://support.microsoft.com/en-us/office/graphics-visuals/reduce-the-file-size-of-a-picture-in-microsoft-office
• CodeTwo knowledge base, How to disable image compression in Outlook (menu path, version requirement, new Outlook limitation; vendor source): https://www.codetwo.com/kb/disabling-image-compression-in-outlook/