Hi @ Enzo Tech,
To better solve this issue, I would like to confirm what your email account type is?
If your account is Exchange online, I recommend that you verify the following in your tenant:
1.Whether authenticated SMTP is enabled for the affected user
-Navigate to Active users - Microsoft 365 admin center
-Select the user you want to test with.
-Make sure Authenticated SMTP is selected.
2.Verify that security defaults are disabled in your organization.
3.Disable Multi Factor Authentication (MFA) on the licensed mailbox being used:
-In the Microsoft 365 admin center, in the left navigation menu choose Users > Active users.
-On the Active users page, choose Multi-factor authentication.
-On the Multi-factor authentication page, select the user and set the Multi-factor auth status to Disabled.
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