Final update: Well, that's a bust. It's definitely a computer-specific issue, as I just reinstated Winmail on a cheap tablet that I primarily use for testing, and imported the same two .iaf files that I used for testing, and it worked without a hitch. Grrr. They both ran the same build of windows, except one was 32-bit and the other 64. Both are on the same network, with the same DNS used. I've cleared the DNS resolver cache before trying on both machines, and it's really annoying that it's not working as I think it should. And no, copying over the folder/registry key didn't work.
I am not running a partition restore because I'm too stubborn -- there's no way I'm doing something that drastic just for an e-mail program. It's definitely not going to get its way by throwing a tantrum, and yes, I know how ridiculous that sounds -- arguing with a nonsentient program, but it's not outwitting me I can tell you that. [Edit: Windows = 1; me = 0. Not sure what's going on, but there's probably some esoteric setting toggled somewhere.]
Next steps? Unfortunately running the traffic through Fiddler was not possible, as even though the proxy settings work for IE, the traffic was
not being rerouted to Fiddler when sending/receiving mail -- whether through the rejected domains of mail.aol.com, mail.gmail.com, smtp.aol.com, and smtp.gmail.com, or through the working Comcast domains. I installed Thunderbird to see if it was a system-wide issue, and it's not. Using another user account/profile on the system, I reinstated Windows Mail, and the same problem persists. Disabled Windows Firewall and Windows Defender, and still no change. I also ran SFC and DISM to repair any corrupted files, and still nothing. The last thing I've tried is an install of Windows Live Mail (through
Microsoft Essentials 2012 from archive.org), as it runs through almost the same path as Winmail does, but the same error occurred with the same level of scant information.
After enabling IMAP logging under the Troubleshooting section (Tools>Options>Advanced>Maintenance), I've determined that the underlying issue is the Microsoft Unified Security Protocol Provider, i.e., SCHANNEL, but a solution isn't found yet. This
thread seemed promising, but unfortunately the digital signature wasn't my issue. Here's the relevant log fragment with the timestamps removed:
[db] Connecting to 'imap.gmail.com' on port 993.
[db] OnNotify: asOld = 0, asNew = 2, ae = 0
[db] srv_name = "imap.gmail.com" srv_addr = xxx.xxx.xxx.xxx:993
[db] OnNotify: asOld = 2, asNew = 3, ae = 1
[db] OnNotify: asOld = 3, asNew = 4, ae = 0
[db] Negotiating secure connection with 'Microsoft Unified Security Protocol Provider'.
[db] OnNotify: asOld = 4, asNew = 6, ae = 2
[db] OnNotify: asOld = 6, asNew = 6, ae = 4
[db] Connection to 'imap.gmail.com' closed.
[db] OnNotify: asOld = 6, asNew = 1, ae = 5
[db] Connecting to 'imap.gmail.com' on port 993.
[db] OnNotify: asOld = 1, asNew = 4, ae = 0
[db] Connection to 'imap.gmail.com' closed.
[db] OnNotify: asOld = 4, asNew = 0, ae = 5
[db] ERROR: "Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity.", hr=800ccc0f
Honestly, I should just stop spending all this effort and give in to a simple partition restore, but I've the time, and, for the moment, and curious enough to try and find the root of the problem. I'm sure in due time I'll just call it a day, but at least I know have a specific starting point other than just a Windows Mail error. For the general end user though, my issue has nothing to do with Windows Mail as reinstated by your well-laidout guide, so I will stop spamming this thread with a me-specific issue. Thanks for your time and consideration, endeavor. While we didn't get anywhere, it's amazing how much effort you put into helping complete strangers across the interwebs.
[Edit: Leaving the last paragraph here so that the subsequent posts will make sense.]By the way Endeavor, not that I need it as I'm advanced enough to know where to go and what to do, but can you make a text equivalent of which options to check in Folder Options (post 1), and how to change ap defaults (post 2)? Would be useful for people who can't see screenshots like me, but may be useful for other people in other scenarios as well.