In this article will discuss different methods to fix – “550 5.7.1 Client does not have permissions to send as this sender” this issue.
Follow the below methods
This issue can occur for several reasons.
Mostly comes when the from email address does not match the username.
So, always check the value firstname.lastname@example.org is the same on user and from.
Generally it works and if didn’t work then you need to contact the email server company and let them to create a shared account and add SendAs privileges for the account.
If above solution didn’t helps then you need to check the “sender” address which is being used by our Phone system which might differs from both the from address and the address/account being used to authenticate with 365 in the IIS relay.
If you are using authenticated relay, then you need permissions in order to send as/on behalf of another user. Instead, you can try configuring the “direct send” method as detailed in this article:
Open the Exchange Management Console and select the user.
Then Right Click and see the option – send as permissions… Here you need to check that User NT AUTHORITY\SELF is listed. If not then add it.
Most frequent workaround, to check the box ‘Accept any sender’ for authenticated users. See the below image: