Exchange server(2007/2010) Default receive connectors

So, we have 2 Exchange

both default receive connectors Permission Group Anonymous was UNCHECK ...
Than all of a sudden someone out of our organisation receive this error
#530 5.7.1 Client was not authenticated ##

i check both Anonymous,

2 questions
how come out of the blue they start receiving this error

Anonymous must be CHECK or UNCHECK ?

Thanks !
Victor CharpentierIt technicianAsked:
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What client they are using,  check the below article for permission, you will get an idea why it happened.
Victor CharpentierIt technicianAuthor Commented:

So do we have to check it or unckeck it ?
you will need to check as it is the default permissions on the receive connector. not sure why you didnt checked it earlier.

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