If a hornet.email user has not send mails via smtp in the last 45 days the account will be marked as inactive which prevents the user to send mails.

When trying to send a mail from an inactive hornet.email user following SMTP-Error will show:

554 5.7.1 - SASL login name rejected.

To activate the User again you will have to login to the control panel with this user. Once logged in the user is active again and sending is allowed right away.

If you still run into issues you can reach support via: support@hornetsecurity.com or chat on this page.