"SMTP authentication disabled" or error 5.7.139
This error means your email provider's administrator has disabled SMTP authentication at the organization level. This is common with Microsoft 365 accounts and is NOT a password issue — regenerating your App Password will not fix it.
Error codes you may see:
- 5.7.139 — SMTP client authentication disabled for the tenant/organization
- 5.7.57 — Client not authenticated, SMTP AUTH disabled
- 5.7.3 — Authentication unsuccessful, SMTP AUTH blocked by policy
- 'Basic authentication is disabled' — Security Defaults are enabled in your org
How to fix (requires your IT admin):
For Microsoft 365:
- Your admin must go to Microsoft 365 Admin Center (admin.microsoft.com).
- Navigate to Users → Active Users → Select your account.
- Click the Mail tab → Manage email apps.
- Check the box for 'Authenticated SMTP' and save.
- Wait 15-30 minutes for the change to propagate.
If your organization has Security Defaults enabled (common for new M365 tenants):
- Your admin must go to Azure Portal (portal.azure.com) → Microsoft Entra ID → Properties.
- Click 'Manage Security Defaults' at the bottom.
- Set 'Security defaults' to Disabled (note: this reduces security for the entire org — discuss with your IT team).
- Alternatively, create a Conditional Access policy that exempts SMTP AUTH from MFA requirements (more secure than disabling Security Defaults entirely).
For Google Workspace:
This error is rare with Google, but if you see it:
1) Your admin must go to admin.google.com → Apps → Google Workspace → Gmail → End User IMAP/POP Access.
2) Ensure IMAP access is enabled for your organizational unit.
3) Check that 'Allow users to manage their App Passwords' is enabled under Security → Authentication.
Note: This is a server-side policy change that only your IT administrator can make. WarmySender cannot bypass organization-level security policies. Send your admin the steps above or forward them this guide.