Can't get SMTP auth (or IMAP, at all) working on an Office 365 E1 account

Question

I'm an IT guy so I'm a bit mystified by this problem. Not an exchange online expert by any means but I'd say I'm an advanced intermediate. I set up exchange online for clients all the time and troubleshoot what are probably 'basic' issues with no trouble. But I'm stuck here.

I am trying to set up SMTP Auth so that a 3rd party app (Stripe) can send out emails via my account. I have IMAP and SMTP Auth enabled on my exchange online plan, and I have generated an app password (but also have tried using my real password). The guy setting this up for me reports that it looks like port 587 is blocked, which I've told him makes no sense. But I can't get my email account set up in thunderbird using the correct password or the app password. It works fine an an exchange account everywhere.

Any suggestions on where to start? I've looked at 100 online articles about SMTP being deprecated and a dozen other possible causes but I don't know which are even pertinent in July 2025 (or to make sure this setup continues to work in the future, too, pending other things that microsoft may or may not turn off in the future).

Thanks!

Answer 1

Hello Cameron,
It has been a while and I am writing to see how things are going with this issue. Have you had a chance to check the replies provided? Any update would be appreciated. 

Please feel free to let me know if there’s anything I can assist you with. 

I look forward to hearing from you soon.

Wish you have a great day. 

Best Regards,  
Viego An  - MSFT | Microsoft Community Support Specialist.

Answer 2

Hello Cameron,

Thank you for your response. 

Microsoft has officially disabled Basic Authentication, so currently there’s nothing broken on your end regarding SMTP Auth, it’s simply no longer supported in the way it used to be.

You've clearly done thoughtful and careful research into this, and that’s appreciated. Microsoft strongly encourages everyone to migrate to Modern Authentication (OAuth2), which is more secure and supports multi-factor authentication (MFA).

As a moderator, I can provide workarounds and share information to the best of my ability. However, for deeper assistance, especially with implementing OAuth2 or resolving tenant-specific issues, I recommend submitting a support request ticket to Microsoft. Their support team can offer more tailored and efficient help for your setup.

Here is how to contact Microsoft Support team:

Contact Microsoft Support 

1. Submit a Service Request: The Global Admin should create a service request with Microsoft support to get advanced technical assistance and diagnostics. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.
2. Find Your Microsoft 365 Admin: If you’re unsure who the Global Admin is within your organization, you can find guidance on locating them here: How do I find my Microsoft 365 admin? - Microsoft Support.
3. Call Microsoft Support: For additional assistance, use this link to find the appropriate contact number: Global Customer Service phone numbers - Microsoft Support

We hope this helps clarify the situation. Please feel free to reply with the requested details so we can continue to assist.
Best regards,

Viego An - MSFT | Microsoft Community Support Specialist.

Answer 3

Yeah I saw all of that various information as I was doing my research. That doesn’t seem to indicate that it should be broken currently, right?

Answer 4

Dear Cameron,

Thank you for reaching out to the Microsoft Support Community. We’re happy to assist you with your inquiry.

I wanted to provide you with an update regarding the upcoming changes to Basic Authentication for SMTP Auth in Exchange Online, specifically in light of the new timeline for July 2025 and beyond.

Microsoft is in the final stages of deprecating Basic Authentication for SMTP Auth, and the new enforcement timeline is as follows:

• March 1, 2026: The start of rejection rollouts for Basic Authentication.
• April 30, 2026: Full enforcement of this change.

What does this mean for you?

• App passwords (which rely on Basic Authentication) will no longer work after the enforcement.
• OAuth 2.0 will be the required method for SMTP Authentication going forward.
• Even if SMTP Auth is enabled at both the tenant and mailbox level, using app passwords (or your regular password) will no longer work unless your client supports OAuth 2.0.

For more detailed information and to ensure you're fully prepared, I recommend reviewing the following resources: https://techcommunity.microsoft.com/blog/exchange/exchange-online-to-retire-basic-auth-for-client-submission-smtp-auth/4114750

If you need any further assistance or have additional questions, please don’t hesitate to reach out. We’re here to help!

Best regards,

Viego An - MSFT | Microsoft Community Support Specialist.