[SGVLUG] Need a qmail "expert"

[Emerson, Tom (*IC)]

I've got a strange problem with a system that uses qmail.  Messages sent to a specific EXISTING user are getting bounced with "no mailbox here with that name"

Messages to other existing users are fine; aliases set up via ~alias/.qmail-aliasname work when sending to other users within the system.  I did find one interesting twist to it: if messages are sent to another domain, the other domain may reject them in funny ways - for instance, I've got an interesting log file that essentially states:

   receiving message for aliasname at domain from tom.emerson at wbconsultant.com
   sending new message to tom.emerson at wbconsultant.com
   remote host said "571 - invalid IP"
   bouncing message to tom.emerson at wbconsultant.com
   remote host said "OK"

Upon looking up error "571", it seems to be an anti-spam result code related to SPF.  Because my original message came FROM "tom.emerson at wbconsultant.com", the server receiving the message saw the sender as myself instead of @domain; looked up the sender's "authorized hosts", and found the IP address didn't match.  Because the BOUNCE came "from" @domain, however, it was allowed through.

But that seems to be a side issue - what would prevent qmail from delivering to an existing local user?

One hitch to this story - it seems the UID for this user was previously used  (multiple admins over time using different tools to set up accounts - namely, the command-line "adduser/useradd" command vs. the web/gui based "webmin" program) - UID's generated by one start at 500, while the other program starts at 1000.  It seems that one or the other of these was used to create a user with a previously existing UID.  The "overwritten" user wasn't actually used anyway (and I've since deleted the account's /home directory) but could this be a potential problem here?