Hi I have Excahnge 2010 SP2. But I try to use POP3 account ,I got error "550 5.7.1 Client does not have permissions to send as this sender" When I send out to external. Let me know how to solve this issue.

Hello Check this: 1) the NT_Authority\self resolution has more details than presented. Charlie on another forum gave this clue: go the the Exchange management console and select the user. Right Click, go to the send as permissions option.. check that User NT AUTHORITY\SELF is listed. If not add it. 2) Another user identifed the following power shell as necessary [PS] C:\Windows\system32>add-adpermission "ConnectorName" -User "domain\user or group" -ExtendedRights ms-Exch-S MTP-Accept-Authoritative-Domain-Sender Note the double quotes when your connector has a space in it. aka "domain users" You have to perform this on both your internal and external connector, then restart the transport and hub services. These steps were left off many forums. Note the '-' in front of ExtendedRights. This was originally presented without this '-' and there is a command -AccessRights ExtendedRight which lead many to a goose chase. 3) The discussion above is about one user having sendas on another. The topic was about the actual User1 not being able to send as 'User1' whereas the dialog was User2 sending as User1. The above steps are for User1 not being able to send as User1. 4) If you get an error, it is necesary to remove the account or repair it within Outlook, or else the error will 'stick' until you do. 550 5.7.1 Client does not have permissions to send as this sender BR Marjan R.