Mail missing for user, finding both Inbox and INBOX

Problem reported by mh - 9/2/2026 at 2:03 PM

Submitted

Hello -

We upgraded to 9735 on Aug 28th, running on Ubuntu in a docker. I have a user reporting since then that emails were missing from several folders. He is using Outlook over IMAP, and when clicking on a folder it will briefly show emails, and then they disappear. Once this happens, he never sees them again. I can find those emails no longer in his Mail\Inbox\folder-name but instead is in Mail\INBOX\folder-name. I can move them back, but have to detach and attach the user for it to really rebuild and see things. Afterwards I removed the INBOX and kept only the Inbox.

Now a few hours later I think he's gone back to his desk to test, and I see Inbox and INBOX both on the server. I don't see any files in the subfolders under INBOX, only folder names, but it's a bit concerning. Has anyone else run into this?

5 Replies

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Derek Curtis Replied

9/3/2026 at 6:59 AM

Employee Post

Does this user have an email client connected to their mailbox? If so, it's possible the client has an INBOX folder, and when they connect, it's being recreated in webmail.

Derek Curtis

CCO

SmarterTools Inc.

www.smartertools.com

mh Replied

9/3/2026 at 10:11 AM

They are using Outlook over IMAP. They can see all of the folders, and have been able to do so for quite some time (years). But this past week when going into a folder it should show the email in Outlook, then it would all disappear. This is when I found both folders in Smartermail, and their missing stuff had been moved to the other.

From talking to them today, everything still looks like it's staying where it belongs. In Webmail they show only "Inbox" and there is no "INBOX". I do see some folders recreated in the SmarterMail side (INBOX), but no actual emails moved over to it, and it's far less than it had been. The rest stays in Inbox.

Right now I think they're good, and the only person I've heard of having the issue. Was just a bit weird.

Nathan Replied

9/3/2026 at 2:48 PM

We have encountered the same or similar issue in an earlier version. I did open a ticket but was advised the Linux version treats Inbox and INBOX as different folder names as the filesystem is case sensitive. At this point I frankly gave up as it is strange to introduce case sensitivity (surely SM should normalise) in a mailbox and I did not have the time or will to argue that it seems like an odd design decision.

Interestingly Webmail only displayed an 'Inbox' folder, the 'INBOX' folder was hidden but present in the user's mail folder. This kind of conflicts with the support statement that 'overlapping' folders can occur due to case sensitive folders being supported on Linux. Looking at the file system the user's missing mail was orphaned in INBOX.

It would be nice if this could be fixed - it must be possible to normalise all underlying folders on disk to say lowercase but have case sensitivity for user consumption in the folders.json files.

I hypothesized the issue is due to some clients having a 'prefix' (if I recall correctly) which is specified as INBOX. I think I have seen this in Thunderbird or maybe old Outlook versions.

Tim Uzzanti Replied

9/3/2026 at 6:21 PM

Employee Post

What support said is true, but we also have code to avoid that. I’ve asked my development team to look into it.

Tim Uzzanti

CEO

SmarterTools Inc.

www.smartertools.com

Nathan Replied

9/4/2026 at 12:59 AM

Thanks Tim, the fix/change sounds like good news.

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