14 Common Issues with SMTP Office365 Com Modern Authentication and How to Fix Them

When it comes to email communication, SMTP, Office365, and Modern Authentication play crucial roles. However, users often encounter various issues while using these services. In this blog post, we'll discuss 14 common problems and their solutions to help you troubleshoot and resolve them efficiently.

1. SMTP Authentication Failure

Authentication failure is a common issue when setting up SMTP for Office365. This usually happens due to incorrect credentials or misconfigured settings. To fix this, ensure you're using the correct username and password, and double-check your SMTP server settings.

【AOTsend Email API】：AOTsend is a Managed Email Service for sending transactional emails. Support Email Types: reminders, authentication, confirmations, notifications, verification codes, invoices, password resets, account activations, billing statements, two-factor authentication (2FA), and one-time passwords (OTP) emails, etc. $0.28 per 1000 Emails. 99% Delivery, 98% Inbox Rate.

You might be interested in:
Why did we start the AOTsend project, Brand Story?
What is a Managed Email API, How it Works?
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?

2. Office365 Connectivity Issues

If you're facing connectivity problems with Office365, it might be due to network restrictions or firewall settings. Check your network configuration and make sure Office365 URLs and IP addresses are not blocked.

3. Modern Authentication Not Working

Modern Authentication enhances security but can sometimes cause issues. If you're facing problems with Modern Authentication, ensure it's enabled in your Office365 tenant and that your application or device supports it.

4. SMTP Timeout Errors

SMTP timeout errors can occur due to various reasons, such as slow network connections or server overloads. To resolve this, increase the timeout settings in your SMTP configuration or contact your email provider for assistance.

5. Office365 Email Delivery Delays

If you're experiencing delays in email delivery, it could be due to high server load or email filtering policies. Check your Office365 message trace to identify any potential bottlenecks.

6. SMTP Relay Not Working

SMTP relay issues can arise from incorrect configuration or permission problems. Ensure your SMTP relay is set up correctly and that the necessary permissions are granted.

7. Office365 Inbox Rules Not Working

If your Office365 inbox rules are not working as expected, it might be due to conflicts or incorrect setup. Review your rules and make sure they are configured properly.

8. Modern Authentication Loop

Sometimes, users might get stuck in a Modern Authentication loop. This can be resolved by clearing cookies and cache or trying a different browser.

9. SMTP Error 550

Error 550 typically indicates that the recipient's mailbox is full or unavailable. Contact the recipient to check their mailbox status or try sending the email again later.

10. Office365 Email Sync Issues

Email sync problems can be caused by various factors, including network issues or device compatibility problems. Check your internet connection and device settings to resolve this.

11. SMTP TLS Negotiation Failed

TLS negotiation failures can occur due to mismatched encryption settings. Ensure both the sending and receiving servers support the same TLS version and cipher suites.

12. Office365 Attachment Size Limit

If you're unable to send large attachments, it's likely due to Office365's attachment size limit. Consider using OneDrive or SharePoint to share large files instead.

13. SMTP Greylisting

Greylisting is an anti-spam measure that can delay email delivery. If you suspect greylisting is affecting your emails, contact the recipient's email administrator.

14. Office365 SPF Record Issues

SPF (Sender Policy Framework) record problems can lead to email delivery failures. Ensure your SPF record is correctly configured to authorize your sending domain.

By addressing these common issues, you can ensure smoother email communication using SMTP, Office365, and Modern Authentication. Regularly reviewing and updating your settings can help prevent these problems in the future.