Outlook shows "?" or "We can't verify the sender"

What it means

In Outlook and Outlook.com, a sender usually appears with their initials or photo. When Outlook cannot confirm who sent an email, it shows a question mark "?" instead, or a note like "We can't verify that this email came from the sender".

Outlook shows this when SPF and DKIM both fail to prove that your domain sent the email, or when DMARC fails. To Outlook, your email looks like it could be a fake.

Why it matters

• Readers trust the email less and may delete it or report it.
• Unverified emails are much more likely to land in the Junk folder.
• Since 2025, Outlook.com is strict with high-volume senders: missing SPF, DKIM or DMARC can lead to outright rejection.

How to check

Delivmail checks this for you in two ways:

• Send a test email: on the home page, copy your unique test address, send it a normal email from the mailbox you want to check, then open the report.
• Use the Domain scanner: type your domain at /domain-scanner to read your DNS records without sending anything.

In the report, the SPF, DKIM and DMARC lines tell you which one fails and why. In Outlook, you can also open the message, view the message source or headers, and look for the Authentication-Results line.

How to fix it

1. Check SPF. Your domain needs one SPF record that lists every service sending for you. Microsoft 365 users need include:spf.protection.outlook.com.
2. Turn on DKIM. In Microsoft 365, DKIM for your own domain is not always on by default: enable it in the Microsoft Defender portal after adding the two CNAME records it gives you. Do the same in Google Workspace or your newsletter tool.
3. Publish DMARC so Outlook knows your policy:

   v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

4. Fix alignment. The domain people see in the From address must be the same domain (or a subdomain) as the one that passes SPF or DKIM.
5. Avoid sending "as" another domain. If you send with a From address at gmail.com or outlook.com through another service, it can never be verified. Use an address on your own domain.

A special case: "on behalf of"

If the From address and the actual sender differ, Outlook may show "sender@tool.com on behalf of you@yourdomain.com". Setting up DKIM with your own domain in the sending tool usually removes it.

Check that it is fixed

DNS changes are not instant. Most are visible within a few minutes, but some providers take up to 24 to 48 hours.

Send a new test email from the home page: SPF, DKIM and DMARC should all pass. Then send an email to an Outlook.com or Hotmail address you control. Your initials or photo should be back, without the question mark.