Outlook SMTP Settings for Outlook.com, Microsoft 365, and Exchange
Outlook SMTP settings for Outlook.com, Microsoft 365, and Exchange. Server, port, encryption values, and setup steps for every Outlook version.
Outlook SMTP settings depend on which Outlook you use. For Outlook.com (personal), the server is smtp-mail.outlook.com on port 587 with STARTTLS. For Microsoft 365 / Outlook for Business, the server is smtp.office365.com on port 587 with STARTTLS. Both require authentication with your full email address and a recent password (or app password if multi-factor authentication is on). On-premises Exchange uses your local server name on port 587 or 25 depending on the admin setup.
Outlook's SMTP server is what sends outgoing mail. When you set up an Outlook account in any mail client, app, or device, the SMTP details tell it where to deliver mail. This guide covers every Outlook variant (Outlook.com, Microsoft 365, Exchange) with verified server names, ports, encryption requirements, and the authentication gotchas that catch people out, especially around multi-factor authentication.
Outlook SMTP Settings at a Glance
| Account type | SMTP server | Port | Encryption | Authentication |
|---|---|---|---|---|
| Outlook.com (personal) | smtp-mail.outlook.com | 587 | STARTTLS | Full email + password / app password |
| Microsoft 365 (business) | smtp.office365.com | 587 | STARTTLS | Full email + password / app password |
| Outlook 2016/2019/2021 desktop | (uses one of the above) | 587 | STARTTLS | Same as the account type |
| Exchange Online (M365) | smtp.office365.com | 587 | STARTTLS | OAuth or basic auth + app password |
| Exchange Server (on-premises) | mail.yourdomain.com | 587 or 25 | STARTTLS / TLS | Admin-defined |
The differences between Outlook.com and Microsoft 365 confuse a lot of users because both are Microsoft mail products, but they run on separate infrastructure with different server names. Pick the row that matches the account you use to sign in.
Outlook.com SMTP Settings (Personal Accounts)
Outlook.com is the free consumer service formerly branded as Hotmail, Live, and MSN. If your email ends in @outlook.com, @hotmail.com, @live.com, or @msn.com, these are your SMTP settings.
| Setting | Value |
|---|---|
| SMTP server | smtp-mail.outlook.com |
| Port | 587 |
| Encryption | STARTTLS |
| Username | Your full Outlook.com email address |
| Password | Your Microsoft account password or app password |
| Authentication required | Yes |
Outlook.com requires SMTP authentication on every send. If multi-factor authentication is enabled on your Microsoft account (recommended, and default for new accounts since 2024), you cannot use your regular password for SMTP. Generate an app password instead (see the app password section below).
Microsoft 365 SMTP Settings (Business Accounts)
Microsoft 365 (formerly Office 365) hosts business email under custom domains. If your email is on your company's domain and you log in through portal.office.com, you are on Microsoft 365.
| Setting | Value |
|---|---|
| SMTP server | smtp.office365.com |
| Port | 587 |
| Encryption | STARTTLS |
| Username | Your full Microsoft 365 email address |
| Password | Your Microsoft 365 password or app password |
| Authentication required | Yes |
Microsoft 365 supports two authentication types for SMTP:
- SMTP AUTH (basic auth) - username and password, gradually being phased out for security reasons. Still works for client apps but requires the tenant admin to keep SMTP AUTH enabled.
- OAuth 2.0 - modern authentication. Required for new third-party apps connecting to Microsoft 365 SMTP. Most current versions of Outlook, Thunderbird, and Apple Mail use OAuth automatically.
If your IT admin has disabled SMTP AUTH at the tenant level, you cannot send mail via basic auth from any device. You will need OAuth-capable software or an app password specifically for SMTP. Microsoft is moving toward OAuth-only for all new tenants in 2026.
Outlook Desktop SMTP Settings
Outlook desktop (Outlook 2016, 2019, 2021, and the new Outlook for Windows) does not have its own SMTP server. It uses the SMTP details from whichever account type you added. Translation:
- Added a personal
@outlook.comaccount? Outlook uses smtp-mail.outlook.com. - Added a Microsoft 365 work account? Outlook uses smtp.office365.com.
- Added a Gmail account? Outlook uses smtp.gmail.com.
When the Outlook setup wizard runs, it usually fills SMTP settings in automatically. You only need to enter them manually when adding a custom domain or troubleshooting.
How to Manually Set SMTP in Classic Outlook (Desktop)
- Click File > Account Settings > Account Settings.
- Select the account and click Change.
- In the wizard, click More Settings.
- Click the Outgoing Server tab and check My outgoing server (SMTP) requires authentication.
- Click the Advanced tab and enter:
- Outgoing server (SMTP): 587
- Use the following type of encrypted connection: TLS (this is STARTTLS in older Outlook versions)
- Click OK > Next > Finish.
New Outlook for Windows
New Outlook hides the SMTP fields. To change SMTP settings for a non-Microsoft account, click the gear icon > Accounts > Email accounts, select the account, and click Manage > Advanced settings.
Outlook for Mac
Mail > Settings > Accounts > select account > Server settings. Outlook for Mac uses the same SMTP servers above, depending on account type.
Exchange and On-Premises SMTP
If your organization runs its own Exchange Server (rather than using Microsoft 365), the SMTP server is on your internal infrastructure, not Microsoft's cloud.
| Setting | Typical value |
|---|---|
| SMTP server | mail.yourcompany.com or exchange.yourcompany.com |
| Port | 587 (modern), 25 (legacy), 465 (less common) |
| Encryption | STARTTLS or implicit TLS |
| Authentication | Usually integrated Windows authentication on the LAN, basic auth or OAuth from outside |
The exact values depend on how your Exchange admin has configured the server. Ask IT for the SMTP relay address if you are not sure. On modern Exchange (2019+), port 587 with STARTTLS is the default for authenticated SMTP submission.
Outlook SMTP Authentication and App Passwords
This is where most Outlook SMTP issues start. Multi-factor authentication (MFA) breaks legacy SMTP clients that only know how to send a username and password.
When You Need an App Password
You need an app password if:
- Your Microsoft account or Microsoft 365 account has MFA enabled (it usually does).
- The app, device, or script you are configuring does not support OAuth 2.0 sign-in (printers, scanners, older mail clients, custom backend scripts).
If your software opens a Microsoft sign-in window during setup, it supports OAuth and you do not need an app password. If it only asks for a server, port, username, and password, you do need one.
Create an App Password for Outlook.com
- Sign in at account.microsoft.com.
- Click Security > Advanced security options.
- Under App passwords, click Create a new app password.
- Copy the password Microsoft generates and paste it into your SMTP client.
App passwords for Outlook.com are 16 characters long with no spaces.
Create an App Password for Microsoft 365
- Sign in at portal.office.com.
- Click your profile picture > My account > Security info.
- Click Add sign-in method > App password.
- Name the app password (so you can revoke it later if needed).
- Copy the generated password.
App passwords are not visible after creation. If you lose one, delete it and create a new one.
If the App password option is missing on Microsoft 365, your tenant admin has disabled it. The fix is either to enable app passwords at the tenant level, or to use an OAuth-capable client.
SMTP Ports: 587 vs 465 vs 25
Outlook accepts port 587 with STARTTLS by default. The other common SMTP ports exist for historical reasons.
- Port 587 (Submission, STARTTLS) - The current standard for authenticated SMTP submission. Use this unless you have a specific reason not to.
- Port 465 (SMTPS, implicit TLS) - Was deprecated, then re-standardized as a valid alternative in RFC 8314. Some clients and servers still support it. Outlook.com and Microsoft 365 do not officially document port 465.
- Port 25 (SMTP relay) - Server-to-server only. Most ISPs and cloud providers block port 25 from end-user devices. Do not use this unless you are configuring an on-premises Exchange relay.
- Port 2525 - Sometimes used by hosting providers as an alternative when port 587 is blocked. Not supported by Microsoft.
If port 587 is blocked on your network (corporate firewalls, some hotel Wi-Fi), try connecting from a different network before changing the port. Switching ports rarely fixes the underlying connectivity issue.
Microsoft 365 SMTP Send Limits
Microsoft 365 SMTP is rate-limited to prevent abuse. The exact limits matter if you send marketing email or transactional mail from Outlook.
| Limit | Value |
|---|---|
| Messages per minute | 30 (per connection) |
| Recipients per message | 500 |
| Recipients per day | 10,000 (most plans) |
| Max message size | 25 MB (default), up to 150 MB if admin raises it |
| Max attachment size | Same as message size limit |
If you need to send more than 10,000 emails per day, Microsoft 365 SMTP is not the right tool. Use a transactional email service (Mailgun, SendGrid, Postmark, Amazon SES) for high-volume sends. Microsoft 365 SMTP is designed for human-sent business mail, not marketing.
Sending Through Outlook SMTP From Other Apps
A common reason to look up Outlook SMTP settings is sending email from somewhere other than Outlook itself: a multifunction printer, a scanner-to-email setup, a custom application, or an automation script.
Multifunction Printers and Scanners
- Use smtp.office365.com (M365) or smtp-mail.outlook.com (Outlook.com).
- Port: 587, encryption: STARTTLS (sometimes labelled "TLS" or "Yes").
- Username: the full email address you want the printer to send from.
- Password: a generated app password (do not use your real account password).
- Test send before sharing the configuration with the team.
If the printer firmware does not support STARTTLS, look for "TLS Yes" or "SSL Yes" in the manual. Older printers (pre-2018) often only support port 25 with no encryption, which Microsoft 365 will reject. You may need a relay service or a firmware update.
Scripts and Custom Apps
For scripts (Python smtplib, Node nodemailer, Ruby Mail, .NET SmtpClient), the same SMTP values apply. Use an app password rather than your account password, and connect with STARTTLS on port 587.
For higher-volume or transactional needs, switch to OAuth via the Microsoft Graph API instead of SMTP, or use a dedicated transactional mail service.
Common Outlook SMTP Errors
| Error | Cause | Fix |
|---|---|---|
| 0x800CCC0F | Connection dropped mid-send | Check network; retry |
| 0x800CCC78 | Authentication failed | Re-enter password or generate a new app password |
| 0x80042109 | Cannot connect to outgoing server | Confirm SMTP server name and port |
| 535 5.7.3 | Authentication unsuccessful | Use an app password (MFA is on) |
| 530 5.7.57 | Client not authenticated | Enable "My outgoing server requires authentication" in Outlook settings |
| 550 5.7.60 | SMTP AUTH disabled for the tenant | Ask your M365 admin to enable SMTP AUTH or switch to OAuth |
| Connection timeout | Port 587 blocked by firewall | Try a different network; ask IT |
For a broader troubleshooting guide that covers all send failures (not just SMTP), see our walkthrough of Outlook not sending emails.
SMTP Settings for Outlook on Mobile
The Outlook mobile app (iOS and Android) uses Microsoft's modern authentication and does not expose SMTP settings to the user. When you add an account, Outlook negotiates the SMTP details automatically.
If you are setting up a personal @outlook.com account in a different mobile mail app (Apple Mail, Gmail app, K-9, BlueMail), use the same SMTP values from the Outlook.com table above:
- Server: smtp-mail.outlook.com
- Port: 587
- Security: STARTTLS
- Username/password: your Outlook.com email + app password (MFA users)
For Microsoft 365 work accounts on mobile, your IT admin may have enforced device compliance via Intune. In that case, only the official Outlook mobile app will work, regardless of SMTP settings.
Outlook SMTP for Customer Support Teams
When customer support teams send replies from individual Outlook accounts using personal SMTP credentials, three things go wrong over time:
- App password sprawl. Each agent generates their own app passwords for various tools. When someone leaves, dozens of app passwords linger.
- Throttling under load. Microsoft 365's 30-messages-per-minute SMTP limit is easy to hit when an agent sends a batch of responses.
- Deliverability inconsistency. Each agent's SMTP submissions count toward your domain's reputation. One agent with a misconfigured signature or no DMARC alignment can hurt deliverability for everyone.
A shared inbox like SupportBee routes outbound replies through a single authenticated sender with consistent DMARC, SPF, and DKIM. Agents send from the app rather than directly via Outlook SMTP, removing the per-agent send-limit ceiling and the app-password management overhead.
For the broader picture on running customer email through Outlook, see our guide on the problems with using Outlook as a helpdesk.
Outlook SMTP Quick Reference
| Need | Answer |
|---|---|
| Outlook.com SMTP server | smtp-mail.outlook.com |
| Microsoft 365 SMTP server | smtp.office365.com |
| Default port | 587 |
| Encryption | STARTTLS |
| Required auth | Yes (full email + password/app password) |
| MFA on the account? | Generate an app password for non-OAuth clients |
| Send limit (M365) | 30/minute, 10,000/day, 500 recipients/message |
| Port 25 | Server-to-server only; do not use from clients |
| Port 465 | Not officially supported by Microsoft |
Frequently Asked Questions
What is the SMTP server for Outlook? For personal Outlook.com accounts, it is smtp-mail.outlook.com. For Microsoft 365 business accounts, it is smtp.office365.com. Both use port 587 with STARTTLS encryption.
Why does Outlook reject my password for SMTP? The most common cause is multi-factor authentication. If MFA is on, you cannot use your regular account password for SMTP. Generate an app password from your Microsoft account security settings and use that instead.
What is the difference between Outlook.com SMTP and Microsoft 365 SMTP? They are different infrastructures. Outlook.com (smtp-mail.outlook.com) is the free consumer service. Microsoft 365 (smtp.office365.com) is the paid business service hosted on different servers. The settings are similar but the server names are different and you cannot use one in place of the other.
Does Outlook SMTP support port 465? Not officially. Microsoft documents port 587 with STARTTLS as the standard for both Outlook.com and Microsoft 365. Some clients can connect on port 465, but Microsoft does not guarantee support.
How many emails can I send per day through Outlook SMTP? Microsoft 365 caps SMTP submissions at 10,000 recipients per day on most plans and 30 messages per minute per connection. Outlook.com limits are stricter and not officially published, but exceeding around 300 recipients per day on a personal account triggers throttling.
Can I use Outlook SMTP for transactional or marketing email? Not at scale. Microsoft 365 SMTP is built for human business mail. For automated transactional or marketing sends above a few thousand per day, use a dedicated service like Mailgun, SendGrid, Postmark, or Amazon SES.
Why does my printer fail to send through Outlook 365 SMTP? Most likely the printer is using your real account password instead of an app password, or your tenant admin has disabled SMTP AUTH. Generate an app password and check whether SMTP AUTH is enabled in the Microsoft 365 admin center.
Is SMTP AUTH being deprecated? For new Microsoft 365 tenants, SMTP AUTH is disabled by default and the preferred path is OAuth 2.0 via the Microsoft Graph API. Existing tenants can still enable SMTP AUTH but Microsoft is pushing OAuth as the modern standard. Treat SMTP AUTH as a fallback for legacy devices, not a long-term strategy.
Next Steps
For most users, the only Outlook SMTP knowledge needed is the server name, port 587, and STARTTLS encryption, plus an app password if MFA is on. If you are setting up Outlook to send mail and it is failing, start with the Outlook not sending emails troubleshooting guide. If you handle customer support email through Outlook and want to remove SMTP from the equation entirely, look at a team inbox that handles authenticated outbound mail centrally.