More info:
I found the IP address of the SMTP server, entered that. So DNS name resolution is no longer a part of the puzzle. It is clear that the messages are not leaving my network. Nothing was registered at the remote server. My firewall is configured to block WAN side messages entering the LAN, but not the other way around. Everything else I have seems to be able to connect from the LAN side to the WAN side apart from this printer.
These symptoms seem to suggest that the printer is being blocked, or maybe not sending the messages at all. Is there some additional security measures included in the code for the printer which may be blocking this? Is there something I have missed somewhere? I have also swapped routers as well while doing this. I have two high end routers exibiting the same behaviour with this device.
I have a multifunction printer I have used for several years and am generally very happy with it. It's capabilities exceed my needs, but one thing I had set up and did use regularly was scan to email. The same email address I had set up specifically to work with this system cannot be used by the 6605. Further investigation suggests that it cannot locate the server. I have been working with my hosting company, and through tests we can see that the printer does not actually reach the account or start the negotiation. Why it has suddenly stopped is unclear. It does correctly locate the SMTP server.
I am using the last listed firmware: 201604180657
The device is discoverable on my network, and is used by multiple devices, so DHCP is working. However I am very suspicious of the value Unknown coming up beside DNS in the top left of the CentreWare screen. If the printer is unable to access a DNS server then it will not be able to resolve domain names. I do not have any other examples of where the printer needs to access anything externally. I have no other symptoms why it is not working.
It is connected to a router, and the entry for DNS in the TCP/IP page is set to Obtain DNS server address automatically. Even when I manually place a DNS server address in that field the field the section in the top left of the CentreWare web page does not change from: DNS: Unknown.
I note that a few other people have reported similar problems (cannot scan to email) but there is no clear answer. I have reset my network settings, which was one of the potential solutions, no change.
The gateway has DNS set up otherwise my computer would not be working, and I could not access the internet.
Any help or guidance appreciated. Particularly if this is somehow related to the SHA2 security messages all of the support threads point to. However in that case as far as I can see it is connecting to Xerox servers and is specifically related to metering and ordering of consumables. In my case I am not using this area at all, and although following the support threads keep leading me to the same area, I do not think it is relevant to this case.