16 SMTP Office365.com Authentication Unsuccessful Solutions

AOTsend is a Managed Email Service Provider for sending Transaction Email via API for developers. 99% Delivery, 98% Inbox rate. $0.28 per 1000 emails. Start for free. Pay as you go. Check Top 10 Advantages of Managed Email API

When trying to send emails through Office365.com using SMTP, you may sometimes encounter authentication unsuccessful errors. These errors can be frustrating, especially when you're trying to automate email sending or integrate with other services. Fortunately, there are several solutions you can try to resolve these issues. In this article, we'll explore 16 potential solutions to SMTP authentication problems with Office365.com.

1. Check Your Credentials

First and foremost, ensure that you are using the correct username and password for your Office365 account. Sometimes, a simple typo can cause authentication to fail.

2. Enable Less Secure Apps

Office365, by default, might block less secure apps from accessing your account. You may need to log into your account and allow less secure apps in the security settings.

3. Use the Correct SMTP Settings

Ensure you are using the correct SMTP server settings for Office365. The SMTP server address, port number, and encryption type must match Office365's requirements.

4. Update Your Email Client or Library

If you're using an outdated email client or library, it may not support the latest authentication methods. Updating to the latest version might solve the issue.

5. Check Your Firewall Settings

Firewalls can sometimes block SMTP traffic. Ensure that your firewall allows outgoing SMTP connections on the correct port.

6. Two-Factor Authentication

If you have two-factor authentication enabled on your Office365 account, you may need to generate an app-specific password for SMTP authentication.

7. Verify Your Account Status

Make sure your Office365 account is active and hasn't been locked due to suspicious activity or too many failed login attempts.

8. Check for Service Outages

Occasionally, Office365 might experience service outages. Check the Office365 service status page to see if there are any known issues.

9. Contact Office365 Support

If none of the above solutions work, consider contacting Office365 support for assistance. They may be able to identify and resolve the issue for you.

10. Review Your Code

If you're integrating SMTP into a custom application, review your code for any potential errors that might be causing authentication failures.

【AOTsend Email API】：
AOTsend is a Transactional Email Service API Provider specializing in Managed Email Service. 99% Delivery, 98% Inbox Rate. $0.28 per 1000 Emails.
AOT means Always On Time for email delivery.

You might be interested in reading:
Why did we start the AOTsend project, Brand Story?
What is a Managed Email API, Any Special?
Best 25+ Email Marketing Platforms (Authority,Keywords&Traffic Comparison)
Best 24+ Email Marketing Service (Price, Pros&Cons Comparison)
Email APIs vs SMTP: How they Works, Any Difference?

11. Use OAuth 2.0

For more secure and reliable authentication, consider using OAuth 2.0 instead of traditional SMTP authentication.

12. Disable Antivirus or Firewall Temporarily

Sometimes, antivirus software or firewalls can interfere with SMTP connections. Try temporarily disabling them to see if they are causing the authentication issues.

13. Check DNS Settings

Ensure that your DNS settings are correct and that your domain is properly pointed to Office365's servers.

14. Reset Your Password

If you suspect your account has been compromised, resetting your password might help resolve authentication issues.

15. Clear Cached Credentials

If you've recently changed your password, clear any cached credentials in your email client or application.

16. Review Account Permissions

Ensure that your account has the necessary permissions to send emails through SMTP. Sometimes, administrative restrictions can prevent successful authentication.

In conclusion, SMTP authentication unsuccessful issues with Office365.com can be frustrating, but there are multiple solutions you can try to resolve them. From checking your credentials to updating your software, ensuring your firewall settings are correct, or even contacting support, there are various paths to success. With these 16 solutions, you should be able to overcome most SMTP authentication challenges with Office365.com.

AOTsend adopts the decoupled architecture on email service design. Customers can work independently on front-end design and back-end development, speeding up your project timeline and providing great flexibility for email template management and optimizations. Check Top 10 Advantages of Managed Email API. 99% Delivery, 98% Inbox rate. $0.28 per 1000 emails. Start for free. Pay as you go.