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

Edgardo Gho 0 Reputation points
2026-03-11T12:43:19.74+00:00

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.

Outlook | Web | Outlook.com | Settings
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  1. IGYQ 19,185 Reputation points Independent Advisor
    2026-03-12T14:13:28.8166667+00:00

    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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  2. IGYQ 19,185 Reputation points Independent Advisor
    2026-03-11T17:00:06.9666667+00:00

    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.

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  3. IGYQ 19,185 Reputation points Independent Advisor
    2026-03-11T14:52:12.06+00:00

    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.

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  4. IGYQ 19,185 Reputation points Independent Advisor
    2026-03-11T14:02:40.2566667+00:00

    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/

    1. 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.

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  5. AI answer

    2026-03-11T12:43:32.3966667+00:00

    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:

    1. 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
    2. 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:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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