Getting an NDR when sending an internal calendar appointment invitation

I have an SBS 2003 / SP2 server.
There are 5 users.
They are all able to send email internally and externally without any problems.
ADOU user settings for all users email delivery restrictions - message restrictions is set to allow from everyone.
I get the following NDR when sending an appointment invitation using Outlook 2003:

You do not have permission to send to this recipient.  For assistance, contact your system administrator. < #5.7.1>

Who is Participating?

[Webinar] Streamline your web hosting managementRegister Today

FearNoMoreConnect With a Mentor Commented:
If OWA works fine...then the problem is with the user cached credentials.....
.nk2 files can also cause this issue
As a test....recreate the outlook profile and check what happens....
Also make sure that the Outlook profile is in Online mode and not in cached mode
Search for the .nk2 files are delete them on the machine where outlook is installed
Try again
One last test is to recreate a new windows profile for this user and check what happens
Based on these tests we will be able to pinpoint what is causing this issue
What happens when you use OWA to send the meeting request?
Is Outlook 2003 running SP3?
Do these users have any delegates defined in Outlook?
as per above; usually the problem is the "delegates" in outlook.
check on every single users make sure that the "delegates" is setup properly or remove if you don't use it.
Easily manage email signatures in Office 365

Managing email signatures in Office 365 can be a challenging task if you don't have the right tool. CodeTwo Email Signatures for Office 365 will help you implement a unified email signature look, no matter what email client is used by users. Test it for free!

villartechAuthor Commented:
OWA works - I do not get an NDR.
Outlook is at SP3 on both computers.
Either user has any delegates assigned.
Editing my above post....i meant "cached information" and not "cached credentials"

just a very basic one,
does the user send the appointment on behalf of someone else?
villartechAuthor Commented:
Thanks, I will test recomendations in a few days.
The user is NOT sending on behalf of anyone.
villartechAuthor Commented:
Outlook was in cached mode.
Placed back online to resolve.
Thanks for all your help.
All Courses

From novice to tech pro — start learning today.