IMAP woes

[#1]

I'm hoping somebody on here can help me before I pull my hair out completely.
My wife is trying to use IMAP to access her PlusNet email on her Windows 10 laptop.  The problem is that out of about 30 folders under her Inbox, the email client is only showing about 5.  We have tried setting up the account in 3 different email clients, Windows 10 Mail, Outlook 2016 and Mailbird.  All behave in the same way and with the same folders.
I have deleted and recreated her mail profile.
I've tried changing the root folder (\, inbox, Inbox, INBOX)
I've tried finding the folders in the IMAP folder management dialogue
Nothing.
If I manually create a folder of the same name in the email client, all of the correct messages show up in that folder, but as soon as I send/receive the folder disappears again.
This also happened on an older Windows 8 machine.
Microsoft have examined the machine and can find nothing wrong with Outlook.  They believe there is something in the PlusNet IMAP service which may not be fully compatible with modern clients.
PlusNet have been less than helpful, stating that their responsibility stops at Webmail (which does work).  They won't even tell me if they can see any difference between the folders which work and those which don't.
Does anybody on here have any idea what could be causing the problem and how to resolve it?
Thanks
Ian

[#2]

Update.  I have just installed Mozilla Thunderbird and that is doing exactly the same.  How can this not be a PlusNet issue?  That's 2 different machines, 2 different operating systems and 4 email clients all behaving exactly the same!

[#3]

Are the folders displayed the standard ones, Inbox (root /), Drafts, Sent, Deleted/Trash and Spam/Junk? These are subscribed to by default. However additional folders need to be subscribed to to make them show up.
In Thunderbird if you select the Inbox then menu item File and click on Subscribe a window should open displaying the (collapsed) Inbox. Expanding that should list all subfolders with ticked checkboxes on the right for those subscribed to.
If any are not subscribed to try doing so by ticking the boxes. Then click OK. Do they then show up in the account list?

[#4]

Thanks for the response.  The standard folders do show up but I am talking about folders created by us.  In webmail they all show as subscribed but in any email client they do not show in the imap folders list, either subscribed or 'all'.  Only a handful show and they are the same ones regardless of which client.
Ian

[#5]

Using Mozilla Thunderbird, have you confirmed that your additional folders do not show in the window that opens when you carry out the action described in this quote from my previous reply?

Quote from: spraxyt

In Thunderbird if you select the Inbox then menu item File and click on Subscribe a window should open displaying the (collapsed) Inbox. Expanding that should list all subfolders with ticked checkboxes on the right for those subscribed to.

[#6]

Yes. The only folders which show in that list are the ones which are working properly. The same happens in Outlook, Mailbird and Windows Mail.

[#7]

Though I use a different E-mail client (and OS  ), I found that changing from "show subscribed" to "show all" picked up a new folder, which remained when returning to "show subscribed" (after ensuring it was, of course )
Phil

[#8]

I am using Thunderbird on Windows 10 and all of the folders I've subscribed to using the instructions given by spraxyt are working correctly. I'm sure there's nothing wrong with the Plusnet end.

[#9]

Thanks. I have the folder list set to all, not just subscribed.
I don't think it is a general problem with Plusnet but I do think there is something up with this mailbox. If not why would every email client behave incorrectly in exactly the same way?

[#10]

In the Thunderbird account settings, Server Settings there's an Advanced button. In there do you have the Show only subscribed folders option set?

[#11]

Unfortunately not.

[#12]

As you have you checked the value of the "IMAP server Directory" (your root folder) for your client, it should be noted that the path is in the in the following format ./ or ./Inbox or ./INBOX If this setting has an entry start by clearing it and if this fails try the other options.

[#13]

Hi
The correct format is 'Inbox', which I was using.  Out of interest I changed it to './Inbox' and all sub-folders disappeared, so I changed it back.
I have created a new PlusNet mailbox, created a number of sub-folders and set it up in Outlook.  It works perfectly, sync'ing folders whether created in Webmail or Outlook.  This seems to support my idea that the problem is a corruption in the PlusNet mailbox, but I have no idea what I can do about that so am waiting to see if PlusNet will now help.
If anybody knows how I can repair IMAP in a mailbox I'd love to know.
Thanks
Ian

[#14]

Attached are the settings I'm using. Check the fullstop after Inbox - have you got that in your settings?

[#15]

Yes thanks.