In April 2020, Microsoft implemented Office 365 Advanced Threat Protection (ATP). This change can affect email deliverability to Office 365 addresses if you send through Omnisend shared domain.
Why Was This Change Made?
Due to the growing threat of phishing attacks, Microsoft decided that the risk of allowing unauthenticated email is higher than the risk of occasionally blocking a legitimate one. Microsoft now requires sender domain alignment to confirm that emails come from who they claim to.
Does It Impact You?
Since April 2020, if you are using Omnisend's shared domain, you may see an increase in bounce rates for Office 365 recipients. If none of your contacts use Office 365, no action is needed – your campaigns and bounce rates will not be affected.
Protect Your Account
If your contact list includes Office 365 addresses, consider sending through your own signed domain.
In an email client (Outlook, Gmail, Yahoo, or others), only the "From:" domain is visible. Without domain alignment, recipients can't confirm the email actually came from your domain – which is exactly what Microsoft's filters check for.
The screenshot below shows how your sender email appears in Outlook:
Microsoft requires your sender email to align with your sending domain (or subdomain). Once this alignment is in place, Microsoft's filters can confirm you're an authenticated sender and will pass your email.
Once you start sending through your own signed domain, you take responsibility for its reputation. Allow time to warm the domain up. During warm-up, use segmentation and start sending to your most engaged contacts first.
Monitor Your Campaigns and Automation
Monitor your deliverability performance regularly for both campaigns and Automation workflows. Early detection of issues helps you act before bounce rates climb.
You can track open, click, spam, unsubscribe, and bounce rates over time in Omnisend Reports.
Next Steps
Keep the following in mind before and after signing a custom domain:
Once a custom domain is signed, you won't be able to send to all contacts immediately. The warm-up process is mandatory to maintain the sender's reputation. Skipping it can harm deliverability across all your contacts – not just Office 365 recipients.
Sending from a custom domain is one of the most recommended deliverability practices. Before signing a custom domain, evaluate whether it's the right step for your account.
Follow this sequence to get started:
Identify whether your account will be affected.
Make a decision and, if needed, sign a custom domain.
Warm up your sender reputation by following our good sending practices.
Aim for the best possible deliverability results.
Note: Authentication does not guarantee deliverability to Microsoft. It only ensures your emails aren't rejected solely for lacking authentication.
For more details, see the official Microsoft article on anti-spoofing protection.
Our 24/7 Support Specialists are here to assist you with any questions through the in-app chat or at [email protected].