You may need to send emails from a specific server for security, compliance, or network routing reasons. Each email account in Outlook can be set to use a unique outgoing mail server. This article explains how to access the advanced account settings and define a custom SMTP server for any account in Outlook.
Key Takeaways: Setting a Custom SMTP Server
- File > Account Settings > Server Settings: The primary dialog for changing the outgoing mail server for any email account.
- More Settings > Outgoing Server tab: Where you configure authentication for the custom SMTP server if it differs from your incoming mail settings.
- More Settings > Advanced tab: Allows you to specify a non-standard port number for the outgoing SMTP server.
Understanding SMTP Server Configuration in Outlook
The Simple Mail Transfer Protocol server is responsible for sending your emails. By default, Outlook uses the SMTP server information provided when you first added your email account. However, you might need to change this. Common scenarios include using a corporate SMTP relay for all external mail, connecting through a VPN that requires a specific server, or using a third-party service for bulk email sending from a specific address.
This configuration is done per account. You must have the correct server address, port number, and authentication credentials for the new SMTP server. These details are typically provided by your network administrator or email service provider. Changing this setting only affects how mail is sent from that account; it does not alter where you receive mail.
Steps to Change the Outgoing SMTP Server
Follow these steps to define a custom outgoing mail server for an email account in Outlook for Microsoft 365 or Outlook 2021, 2019, and 2016.
- Open Account Settings
In Outlook, go to File > Info. Click on the Account Settings button, then select Account Settings again from the dropdown menu. - Select the Account to Modify
In the Account Settings window, on the Email tab, click to highlight the email account you want to configure. Then, click the Change button above the list of accounts. - Access More Settings
The Change Account window shows basic server information. Click the More Settings button in the lower-right corner. - Navigate to Outgoing Server Tab
A new Internet E-mail Settings dialog opens. Click the Outgoing Server tab. Check the box labeled “My outgoing server requires authentication.” - Set Authentication Method
Usually, select “Use same settings as my incoming mail server.” If your new SMTP server needs different credentials, select “Log on using” and enter the specific User Name and Password. You can also select “Log on using Secure Password Authentication” if required by your server. - Change the Server and Port
Click the Advanced tab. In the Outgoing server field, you will see the SMTP port number, usually 587 or 25. To change the server address itself, you must go back. Click OK to close the Internet E-mail Settings dialog, returning you to the Change Account window. - Enter the New SMTP Address
In the Change Account window, locate the Outgoing mail server field. Delete the existing server name and type the full address of your new SMTP server, such as smtp.yourcompany.com or mail.provider.com. - Test and Save
Click Next. Outlook will test the account settings with the new outgoing server. If the test fails, verify your server address, port, and authentication. After a successful test, click Close, then Finish, and finally Close again to exit the Account Settings windows.
Common Mistakes and Configuration Limits
Outgoing Server Test Fails Immediately
A rapid test failure often points to a network block. Ensure your firewall or antivirus software is not blocking Outlook or the specific SMTP port. Confirm you are on the correct network, especially if the server is internal and requires a VPN connection.
Emails Stuck in the Outbox
This usually indicates an authentication error or incorrect port. Revisit the Outgoing Server tab and verify the login credentials. On the Advanced tab, try the alternative SMTP port 465 with SSL encryption, or port 587 with TLS encryption, as required by your server.
Can’t Change Server for Microsoft 365 or Exchange Accounts
For modern Microsoft 365 or Exchange accounts using automatic setup, the outgoing server field may be grayed out. This is because sending is managed directly by the Exchange server. To use a different SMTP path, you may need to contact your administrator or set up the account as a different account type, like POP/IMAP, which allows manual server configuration.
Manual vs. Automatic Account Setup Comparison
| Item | Automatic Setup (Default) | Manual Setup (POP/IMAP) |
|---|---|---|
| Outgoing SMTP Server | Typically locked and managed by Microsoft 365/Exchange | Fully editable field in account settings |
| Configuration Flexibility | Low, server settings are auto-discovered | High, allows custom ports and servers |
| Best Use Case | Standard Microsoft 365, Outlook.com, or Exchange Online accounts | Third-party email (Gmail, Yahoo), corporate SMTP relays, or specialized sending needs |
| Authentication | Uses modern OAuth 2.0 by default | Often uses basic username/password or SPAs |
You can now direct email from a specific account through a designated SMTP server. For related control, explore creating separate Outlook profiles for accounts with completely different sending requirements. A useful advanced tip is to use the Test Account Settings feature in the Change Account window after any network change to verify connectivity instantly.