We have a MFC - Kyocera Bizbub C284. On a 2012 server, we have a share called scan, and a local account called scanner. No matter what combination of username I try, (scanner, \scanner, SERVER\scanner) I'm unable to scan to SMB as it fails with an authentication error, and yes, I have the correct password :-)
When I use my domain account (DOMAIN\userid), I can scan to the same share without issue.
I have manually mapped the share using the local account, and verified the scanner account has read/write/delete access to the share.
We also have a 2008 server, using a local account SCAN to SMB from the same MFC works.
I've done a bit of research and it appears might be related to be the hardening of the WS2012 environment, however don't understand why a domain account works and a local account doesn't. I'd expect it to work or fail on both accounts, not be mutually exclusive.