SMTP Settings
Server:smtp-mail.outlook.com
Port:587
Security:STARTTLS
IMAP Settings
Server:outlook.office365.com
Port:993
Security:SSL
Rate Limits
Per Day300 emails
Recipients per Message100
Outlook.com: 300 recipients/day, 100 recipients/message. Microsoft 365: 10,000 recipients/day.
Authentication Requirements
- SPF record required
- DKIM strongly recommended
- DMARC policy helps deliverability
- Valid reverse DNS (PTR) record
- TLS 1.2 or higher
Deliverability Tips for Outlook / Microsoft 365
- 1Register with Microsoft SNDS (Smart Network Data Services)
- 2Implement all authentication protocols (SPF, DKIM, DMARC)
- 3Join the Junk Email Reporting Program (JMRP)
- 4Maintain consistent sending patterns
- 5Use dedicated IPs for high-volume sending
- 6Monitor feedback loops for complaints
Common Issues & Solutions
Emails blocked (550 5.7.1)
Check if your IP is on Microsoft's blocklist, review SNDS data, and submit a delisting request if needed.
Going to Junk folder
Improve sender reputation, ensure proper authentication, and ask recipients to add you to contacts.
Connection timeouts
Verify your sending IP has proper PTR records and isn't on any blocklists.
Quick Reference
- Provider
- Outlook / Microsoft 365
- Market Share
- ~10% of global email
- SMTP Port
- 587
- Security
- STARTTLS