This occurs when the SMTP server settings are set to use authentication but the client is not being authenticated by the email server. There may be multiple reasons for this such as:
The client (the computer hosting the TaskCentre Server installation) does not have permissions on the email server to send messages.
The username or password in the SMTP Server settings are incorrect.
The SMTP server settings are found by following these steps:
Log in to TaskCentre.
Click Tools, Output.
Click Send Message (SMTP).
Verify that the SMTP server settings and the credentials listed in the SMTP server settings are correct.
This can be done by logging in to the email account listed in the SMTP Server settings using the credentials listed.Also, to test the connection, click Test Connection. However, logging in to the account is a more reliable indication of whether the credentials are correct or not.
This error comes form the email server. Following verification that the SMTP server settings and credentials are correct, this should be investigated further by your IT provider.