why do my emails end up in spam when sending to gmail

Gmail decides whether each message reaches the inbox, so for a personal Outlook.com address the practical fix is to have the Gmail recipient mark the message Not spam, add you to Contacts, and then reply to a simple test message.

If you use @outlook.com, @hotmail.com, or @live.com

You cannot configure SPF, DKIM, or DMARC yourself for these Microsoft-owned domains; Microsoft manages their DNS authentication records. Gmail also considers authentication, sender reputation, message content, and recipient interaction when classifying mail.^1^

Try this sequence:

1. Send one plain-text test message to the Gmail recipient:
   • Use a clear subject.
   • Remove the signature, links, images, and attachments.
   • Send it to one recipient only—do not use BCC.
2. In Gmail, ask the recipient to:
   • Open Spam.
   • Select your message and choose Not spam.
   • Add your Outlook.com address to Google Contacts.
   • Reply to the message.
3. Avoid sending the same message repeatedly or sending many messages at once. Microsoft specifically recommends reducing volume, avoiding large BCC lists, and sending to people who read or reply to your messages.^2^
4. If the plain test succeeds, add your signature, links, or attachment back one at a time. Outlook.com documentation notes that signatures can sometimes affect delivery; this isolates the element triggering filtering.^3^

A previous Outlook.com problem involving certain country-specific Microsoft domains and Gmail was fixed in August 2024. Therefore, adding an @outlook.com alias is not the current general remedy unless Microsoft Support identifies a recurrence.^4^

If Gmail rejects the message instead of placing it in Spam

Check the complete non-delivery report for an SMTP error such as 550 5.7.1. A rejection and delivery to Spam are different outcomes:

• Delivered to Spam: use the recipient-interaction and simplified-message steps above.
• Rejected with an error: preserve the full report, including the diagnostic text and timestamp, and contact Outlook.com Support through Outlook.com → Help → Still need help? Microsoft states that spam filters on the recipient server can cause non-delivery reports.^3^

If this happens with only one Gmail recipient, their individual filtering and interaction history are likely relevant. If it happens consistently across several unrelated Gmail accounts, include examples from multiple recipients when contacting support.

If you send from a custom domain through Microsoft 365

For an address such as [Email], the domain administrator should validate SPF, DKIM, and DMARC. SPF identifies authorized sending servers, DKIM signs messages, and DMARC checks alignment with the visible From domain; Microsoft recommends that these mechanisms work together.^5^

Google requires SPF or DKIM for all senders. Higher-volume senders—about 5,000 or more messages per day to personal Gmail accounts—must meet additional requirements, including SPF, DKIM, DMARC, TLS, and valid reverse DNS.^1^

The administrator should:

1. Inspect the Gmail message’s Authentication-Results header.
2. Confirm that SPF and DKIM pass and that at least one aligns with the From domain.
3. Validate the DMARC record and reporting address.
4. Register the domain in Google Postmaster Tools to review authentication, reputation, spam rate, and delivery errors.^6^
5. If these are newsletters or other bulk mail, use a dedicated authenticated subdomain and provide an unsubscribe mechanism. Microsoft 365 treats bulk sending as best-effort rather than a supported primary use.^7^

References

1. Email sender guidelines - Gmail Help - Google Help
2. Sender Support in Outlook.com | Microsoft Support
3. Can't send or receive email in Outlook.com | Microsoft Support
4. Fixes or workarounds for recent issues on Outlook.com | Microsoft Support
5. How email authentication works in Microsoft 365 - Microsoft Defender ...
6. Set up Postmaster Tools - Gmail Help - Google Help
7. Outbound spam protection for cloud mailboxes