Microsoft Deliverability and Design Tips

Microsoft owns common email domains including, but not limited to:


These domains are grouped together in your Sendlane dashboard under “Microsoft.”

Microsoft is known for its robust filters and security features that protect its users from unwanted email communication.

You may have noticed that Microsoft email addresses tend to have lower open, click, and conversion rates than other email providers. You may have also noticed that your email content looks off when viewed in Microsoft accounts compared to other inbox providers.

These content and deliverability quirks happen because Microsoft’s security features and the varied rendering process used by its apps (mobile and desktop) can end up blocking or not rendering certain content in marketing emails that users want to receive.

Read on to learn how to optimize your infrastructure and content for Microsoft!

Deliverability Tips

Use an Authenticated Sending Domain

Microsoft is unlikely to deliver your email without an authenticated sending domain or standalone SPF record set up. Authenticated sending domains provide DMARC authentication to your “from” email.

Microsoft formerly quarantined non-authenticated domains in the junk/spam folder, but as of 3/22/23, “will now honor the DMARC record of “p=reject” by rejecting the message [entirely] if the domain fails DMARC.”

Authenticated sending domains include SPF, DKIM, and DMARC authentication, in that order. DMARC is the last check before an email is ultimately rejected, accepted, or quarantined by an inbox provider like Microsoft.

🙋  Why do my emails sent from an authenticated sender say "on behalf of" in the Contact's inbox?

Microsoft’s mobile apps and Outlook 365 for desktop use a stricter method for displaying “from” addresses than other inbox providers.

Microsoft ignores the newer RFC 5322 standard used by most other inbox providers, which tells inboxes how to interpret and display authenticated “from” email addresses, in favor of the older RFC 822 standard, which tells inboxes to display the actual sender without interpretation.

Because the “on behalf of” originates with Microsoft, there is currently no way to change this in your Sendlane account. Sendlane's development team is considering possible solutions that may address how Microsoft displays authenticated sending domains in certain Microsoft apps.

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Content Issues

Below is a list of adjustments Microsoft makes to how emails display, and tips for avoiding them.

Images are not downloaded by default

Microsoft’s default settings do not download images automatically.

This can result in Contacts seeing an email that looks blank or, worse, full of security warnings if it is too image heavy and they have not turned on automatic image downloading or added you to their always allow list.


  1. Reduce the number of images in your email
  2. Use ALT text for all images in your email
  3. Make all crucial information and calls to action text based

Large images are cropped

Microsoft crops images that are taller than 1728px, leaving a cut off image in the Contact’s inbox.


  1. Use small images
  2. Do not use HTML to resize images; Microsoft will ignore it and render the original image size
  3. Check your image’s dimensions in the email builder

 This image will likely be cropped in Microsoft inboxes and should be resized to a maximum height of 1728px.

 .GIF images do not play

Microsoft does not show a .GIF’s animation. Instead, it renders just the first frame of the .GIF.


  1. Do not use .GIFs to communicate any crucial information
  2. Review your .GIF’s first frame and make sure it fits in with the rest of your email content

Buttons do not match the preview shown in the email builder

Microsoft does not render border radius options, meaning all buttons will be square in Microsoft inboxes.


  1. Preview buttons as both square and rounded if using rounded corners

Colors are not transparent

Microsoft does not support transparent colors and will render them at full opacity.


  1. Do not use transparency in your email design
  2. If you must use transparency, preview your design at your desired transparency and at full opacity

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