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Action Flow "Send Email" module keeps deactivating — auth error with Outlook

  • September 17, 2026
  • 2 replies
  • 9 views
Songfan
Level 5
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Having a frustrating recurring issue and not sure what the actual fix is at this point.

We have several Action Flows that send emails via an Outlook account. Every few days, one or more of them deactivate automatically with this error in the Send Email module:

Invalid login: 535 5.7.139 Authentication unsuccessful, basic authentication is disabled.

Reconnecting the email connection seems to help temporarily but the error comes back after a few days. Has anyone dealt with this, or found a more permanent fix?

Best answer by m.sanchezmedina

Hi Songfan,

Are you using the generic email module by any chance? If so, I recommend that you use the Microsoft 365 Email (Outlook) module instead. 

The former uses SMTP / basic authentication. It is likely that the Microsoft setup for the account does not support this type of authentication anymore.

The Microsoft 365 Email module supports OAuth which is more secure.

 

Here is the link to a support case caused by a similar error.

 

Best,

Martina

      2 replies

      m.sanchezmedina
      Celonaut
      Forum|alt.badge.img+1

      Hi Songfan,

      Are you using the generic email module by any chance? If so, I recommend that you use the Microsoft 365 Email (Outlook) module instead. 

      The former uses SMTP / basic authentication. It is likely that the Microsoft setup for the account does not support this type of authentication anymore.

      The Microsoft 365 Email module supports OAuth which is more secure.

       

      Here is the link to a support case caused by a similar error.

       

      Best,

      Martina

      Martina Sánchez Medina
        Danieldo
        Level 7
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        • Danieldo
        • Level 7
        • September 17, 2026

        Worth adding, since it's not covered above: if the account you're using is a personal Microsoft account rather than a managed organizational one, the Microsoft 365 admin center isn't accessible at all, so checking or changing the "Authenticated SMTP" setting isn't an option in that case. As far as I know, there's no clean workaround for it, switching to the Microsoft 365 Email module (OAuth) is really the only lever available on the Action Flow side. If that's the situation, it's probably worth flagging directly with support rather than trying to chase down admin settings that aren't reachable.

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