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Outlook (Microsoft 365) SMTP Setup

Outlook has a global business email market share of 22%. It processes around 210+ billion emails daily. Overall, it has ​​400 million active users globally.

Now I am going to share the SMTP methods for Outlook.

Microsoft offers three primary methods for sending emails from devices or apps using Outlook or Microsoft 365. These methods are outlined below:

  • Authenticated SMTP (SMTP AUTH): The user sends emails using mailbox credentials to any recipient.
  • SMTP Relay (Connector): Emails are sent through Exchange Online via a connector. Authentication is required, either through IP address or a certificate.
  • Direct Send: No authentication is needed, but the user can only send emails to Microsoft 365 domains.

Requirements for Microsoft Outlook SMTP​

Before you proceed to the next step, make sure you have the following things to get started.

  • Microsoft account with a mailbox.
  • For SMTP AUTH: App password is necessary when multi-factor auth (MFA) is enabled.
  • For SMTP Relay: Admin access to configure an Exchange Online connector and whitelist IPs.
  • Open outbound ports 25, 587 (TLS) and/or 465 (SSL) on your network firewall.
  • Published DNS records: SPF including include:spf.protection.outlook.com, DKIM, and DMARC for your domain.

Authenticated SMTP (SMTP AUTH)​

You can use this method to send email from your Outlook email or Microsoft 365 mailbox.

Standard Outlook.com / Microsoft 365 SMTP AUTH​

Use this method to send authenticated email from an Outlook.com or Microsoft 365 mailbox.

  • Server or Host: smtp-mail.outlook.com or smtp.office365.com
  • Port (TLS): 587
  • Port (SSL): 465
  • Authentication: Required
  • Username: Full email address
  • Password: App Password or Account Password (if 2FA not enabled)

After inputting all the information properly, send a test message and check for delivery or any unwanted authentication errors.

SMTP Relay via Connector​

This step is suitable for any business app that likes to send bulk email.

  • SMTP Server: smtp.office365.com
  • Ports: 25 (no encryption), 587 (STARTTLS), 465 (SSL)
  • Encryption: Optional, but TLS is recommended
  • Authentication: IP allowlist of TLS certificate
  • Allowed Senders: Any domain that Microsoft 365 accept.
  • Recipient: Both internal and External domain mail

Connector setup (Admin Center):

  1. Go to Admin Center → Exchange → Mail flow → Connectors.
  2. Create a new connector: "Your organization's email server → Office 365."
  3. Choose authentication: IP address of your device/app or certificate.
  4. Restrict senders to your domains and require TLS if desired.
  5. Save and point your device/apps to smtp.office365.com.

Direct Send​

This method can be used for internal notification. You can mail only to the recipients in your Microsoft 365 tenant.

  • SMTP Server: <your-tenant-domain>.mail.protection.outlook.com
  • Port: 25
  • Encryption: None
  • Authentication: Not required
  • Recipient Scope: Only users in your tenant
  1. In DNS, note your MX record (e.g., example-com.mail.protection.outlook.com).
  2. Configure your device/app to send via that MX host on port 25.
  3. Ensure your sending IP is in your SPF record and not blocked.

Sending Limits & Quotas​

You may notice email deliverability issues while sending bulk email, so it's better to take a look at the email sending limitations.

  • Authenticated SMTP: You can send a maximum of 10,000 emails per day to individual recipients and 30 messages per minute.
  • SMTP Relay: You can align with Microsoft 365 sending limits, up to 10,000 recipients/day per mailbox.
  • Direct Send: Subject to standard inbound spam checks; uses tenant limits for internal delivery.

When you exceed this limit, it will trigger throttling or temporary blocks.

That's all about Outlook SMTP settings. Register or login to your Orkap account and set up your desired Outlook SMTP methods.

If you run into any issues during configuration, feel free to reach out to us. Our support team will gladly help you set up Outlook SMTP settings in your Orkap admin panel.