Hello, my name is ***** ***** I will try to assist you tonight.
There may be different reasons of the entourage error 17099. The most common cause of this is having a bad email address your sending to. Please try and send yourself a test email and let me know if that works or not.
Just a couple other things to think about and look at...
Since this is a sending issue, see if there is a message stuck in your outbox that won't get sent? Is there a problem with your ISP which prevents you from sending e-mail messages? Can you verify if you can send messages using a different e-mail client, such as Thunderbird or Apple Mail?
One more thing, I wanted to send you I found, and hope that this might help. But either way please reply and let me know what else I can assist you with. This is from a Microsoft Office for MAC forum.
Relaying to <the email address> prohibited by administrator Email could not be sent Account name (my account name) Error -17099
Error -17099 is an Entourage SMTP Server Reply Error, and is returned when the SMTP server has returned a permanent or transient error or returns an unexpected result code.
This error is coming from your ISP.
Users have reported this error when sending to large groups. ISPs are who limit the allowed number in a group. Usual number is ***** recipients to avoid spammer misuse. Entourage has no limit. You should contact your mail provider to ascertain the maximum number of recipients per message and note it. You can use the free "Split Recipients" script to send a mass e-mail in separate mailings automatically:
Split Recipients for Entourage 2001
Split Recipients for Entourage X
Most ISPs also require you to use their SMTP address when sending.
I hope this additional information helps.
Please let me know how things are going in regards ***** ***** information. Thanks