SME V7.3 with latest updates. Also has dungog enhancements. Last week all mail sent to server from outside returns to the sender a Recipient Unknown error but delivers the email. If email is sent from the inside to the outside it does the same thing. This appears to have happened after an update. If I recreate the user it still gives the same error. Any ideas?
You, or someone, or maybe even a dungog contrib, has enabled the Bcc (keep a copy of all mail) feature, but hasn't created the use 'maillog'. You need to either create the use called maillog, or you need to disable the Bcc feature.
Search here for Bcc or maillog, if this doesn't make sense to you.