Outlook account created on 2026 with Microsoft 365 Basic can't access SMTP

Question

Outlook account created on 2026 with Microsoft 365 Basic can't access SMTP

Edgardo Gho 0

Hi, I created a new account on outlook in february 2026. When I try to setup this account on an email client on my phone (K9) which uses OAuth I can access IMAP or POP, but can't access SMTP. I get: SmtpClientAuthentication is disabled for the Mailbox. Visit https://aka.ms/smtp_auth_disabled for more information.

This is a Microsoft 365 Basic account (not a "free" one). Is SMTP enabled for these accounts? The client I use is able to connect fine to an older account I have with @outlook.com that is free (not basic). So it is not a problem with the email client, but with the account itself.

Peter 0 Reputation points

2026-11-12T16:16:15.0533333+00:00

SMTP AUTH seems to be disabled on personal outlook.com email addresses. Is it possible to provide an alternative method of authentication so that I can use Thunderbird to send emails via SMTP to outlook.com smtp server? At the moment when I attempt to send smtp from Thunderbird I get the following: 535 Authentication unsuccessful,

SmtpClientAuthentication is disabled for the Mailbox

currentAction=_actionAUTH_XOAUTH2

5 answers

Your answer

Peter 0 Reputation points

2026-11-12T16:16:15.0533333+00:00

SMTP AUTH seems to be disabled on personal outlook.com email addresses. Is it possible to provide an alternative method of authentication so that I can use Thunderbird to send emails via SMTP to outlook.com smtp server? At the moment when I attempt to send smtp from Thunderbird I get the following: 535 Authentication unsuccessful,

SmtpClientAuthentication is disabled for the Mailbox

currentAction=_actionAUTH_XOAUTH2

Answer 1

SMTP is available for Outlook.com / Microsoft 365 consumer mailboxes, including new accounts, but it can be disabled at the service side. The error message “SmtpClientAuthentication is disabled for the Mailbox” indicates that SMTP AUTH is currently disabled for that mailbox or tenant, not that the Microsoft 365 Basic subscription type blocks SMTP.

For Exchange Online/Outlook.com mailboxes, SMTP can be disabled either:

At the tenant level
- Check the current setting:
```
     Get-TransportConfig | Select SmtpClientAuthenticationDisabled
```
  - False = SMTP AUTH is not disabled tenant-wide.
  - True = SMTP AUTH is disabled for the whole tenant.
- To enable SMTP AUTH tenant-wide:
```
     Set-TransportConfig -SmtpClientAuthenticationDisabled $False
```
At the mailbox level
- Check the mailbox setting:
```
     Get-EXOCasMailbox <mailbox account> -Properties SmtpClientAuthenticationDisabled | Select SmtpClientAuthenticationDisabled
```
  - Blank = mailbox follows the tenant-level setting.
  - False = SMTP AUTH is enabled for this mailbox (overrides tenant setting).
  - True = SMTP AUTH is disabled for this mailbox.
- To enable SMTP AUTH for a specific mailbox:
```
     Set-CasMailbox <mailbox account> -SmtpClientAuthenticationDisabled $False
```

If SMTP AUTH is disabled at either level, OAuth-capable clients such as K-9 will fail to send mail via SMTP even though IMAP/POP with OAuth works.

If direct PowerShell access to the tenant is not available (for example, for a purely consumer Outlook.com account), this needs to be corrected by Microsoft on the service side; in that case, contact Outlook.com/Microsoft 365 consumer support and provide the exact error text so they can re-enable SMTP AUTH for the mailbox.

Note that Basic authentication is being deprecated across Outlook.com and Exchange Online. For POP/IMAP/SMTP, OAuth 2.0 is supported and should be used, as in the K-9 configuration.

References:

Answer 2

IGYQ 22,340 Independent Advisor

Hi!

Welcome to Microsoft Q&A forum.

Based on your information, for many new Outlook.com mailboxes, Microsoft disables SMTP AUTH by default for security reasons. Some clients like K‑9 Mail require SMTP AUTH to send mail, so sending fails even though receiving works.

Try this one first to check if the settings is available.

Go to: https://outlook.live.com/mail/

Click Settings → View all Outlook settings

Go to Mail → Sync email

Look for Authenticated SMTP

Enable Turn on SMTP AUTH

If the option exists, turn it ON, save, and retry sending.

Edgardo Gho 0 Reputation points

2026-03-11T14:34:45.29+00:00

I dont have any options for Authenticated SMTP. The only options I see are to turn on POP and IMAP. Nothing related to SMTP on any of the settings (checked them all).

Answer 3

IGYQ 22,340 Independent Advisor

If you only see POP and IMAP options and no Authenticated SMTP option in Outlook.com, then your mailbox has SMTP AUTH disabled with no user toggle available. This is common for new accounts created in 2025–2026, including those with Microsoft 365 Basic.

Edgardo Gho 0 Reputation points

2026-03-11T16:24:24.87+00:00

OK, I changed my subscription to Full office 365, and I still dont get the option for SMTP and when I try with K9 I still get the SMTP is not enabled for this mailbox.

I got the OAuth prompt to allow access to the app (so I know this is OAuth for sure). Is it just that outlook wont offer SMTP anymore? Even with paid accounts?
Edgardo Gho 0 Reputation points

2026-03-11T16:34:42.7933333+00:00

To be clear, the subscription is 365 Personal. (no longer basic)

Answer 4

IGYQ 22,340 Independent Advisor

Still the same even with the full subscription(still blocked on server side for Security purposes) Only Business or Enterprise accounts support SMTP AUTH.

You can check and try this if it will work. (Update you K-9 settings)

SMTP Server: smtp.office365.com (instead of smtp-mail.outlook.com).
Port: 587.
Security: STARTTLS.
Authentication: OAuth2.

Edgardo Gho 0 Reputation points

2026-03-11T17:43:49.33+00:00

I tried all settings, and none work, they all have the same issue (SmtpClientAuthentication is disabled for the mailbox). This is pretty lame, I understand free accounts might be limited since they might be forced to use webmail and view ads, but paid accounts not being able to access SMTP is bad.

Answer 5

IGYQ 22,340 Independent Advisor

I understand the frustration. Your configuration isn’t wrong, the error happens because Outlook.com accounts (even paid Microsoft 365 Personal ones) no longer support SMTP AUTH.

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