Remote Server returned '550 5.7.1 Command not allowed'

Question

I have a user that modified a meeting request that was initially sent by her boss.  She has rights to her boss' calendar.  After modifying the meeting request, she received the following undeliverable.  Any idea where to start troubleshooting?
Thanks
Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept email from certain senders, or another restriction
may be preventing delivery.<o:p></o:p>
"domain name" gave this error:
Command not allowed <o:p></o:p>
 

Answer 1

Hi redman71,
Thank you for your question.
We could refer to the following steps to make sure we have grant correct permission for user:
1.Open Outlook 2013.
2.Select Calendar.
3.On the Home tab, select Calendar Permissions.
4.Select the Permissions tab if it is not already selected.
5.Select Add. 
6.Type the name of the person you wish to add (e.g, doe, jane).  Highlight the name that you want to add.
7.Click the Add button and the user's name will display underlined in the text box to the right.
8.Click Ok.
9.Under Permissions you can set the appropriate permissions for the user (e.g., Reviewer, Author, etc.)
10.Click OK when you are finished selecting the permissions.
Permission Settings:
Owner: Create, read, modify, and delete all items, and create subfolders. Can change the permission levels that other people have for the folder. 
Publishing Editor :Create, read, modify, and delete all items and create subfolders. 
Editor: Create, read, modify, and delete all items.
Publishing Author: Create and read items, create subfolders, and modify and delete items and files that you create. (Does not apply to delegates.)
Author: Create and read items, and modify and delete items and files that you create.
We could refer to the following link:
https://technet.microsoft.com/en-us/library/dd298062(v=exchg.150).aspx
If there are any questions regarding this issue, please be free to let me know. 
Best Regard,
Jim
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact [email protected]
Jim Xu
TechNet Community Support