Mailbox created in my app doesn't show up in Mail

In my app it’s possible to upload emails back into an IMAP account. This also creates the mailbox if the mailbox doesn’t exist. For one user the new mailbox doesn’t show up in Mail. My first idea was that the subscribe is missing. But the mailbox still doesn’t show up.

Log from creating the mailbox “upload-Ruby”:

2025-04-24 18:07:39 ImapWithPassword.CheckMailbox verbose log 1:
----IMAP REQUEST----
aaao NOOP
----IMAP RESPONSE----
aaao OK NOOP completed (0.001 + 0.000 secs).
----IMAP REQUEST----
aaap CREATE “Inbox.upload-Ruby”
----IMAP RESPONSE----
aaap OK Create completed (0.066 + 0.000 + 0.065 secs).

List of subscribed mailboxes:

2025-04-24 18:07:40 ImapWithPassword.GetMailboxes subscribed mailboxes: INBOX.Sent
INBOX.Trash
INBOX.Drafts
INBOX.Junk
INBOX.Sent Messages
INBOX.Notes
INBOX.Starred
INBOX.spam
INBOX.Archive
INBOX.Deleted Messages
INBOX.upload-Ruby

Does anyone have an idea what could cause the problem here? And yes, I know that it takes a while until the new mailbox shows up in Mail. We also did a “Synchronise all accounts”.

What mail service is this? If memory serves, once upon a time you could log into the Gmail web interface and selectively turn on/off which Gmail tags would be presented to IMAP clients. I used it to turn off the All Email tag to prevent downloading duplicate messages.

I wonder if it’s an opt-in situation where the user needs to check that box for newly created folders.

It’s not Gmail. The user has a domain with hosted emails. The question is a good one. But how would my software recognise such mailboxes? IMAP only supports subscribing to a mailbox.

In the case of Gmail, the Gmail IMAP service simply omits any tags that the user has deselected from the list of folders it reports to IMAP clients - so they have no way of knowing what’s not being shown.

Do you know what service this user is utilizing? Maybe that would help us understand.

Also - is this a problem with just this one user, or more widely spread?

Hosted domain, no special service. No Gmail, iCloud, Proton.

So far this happened only for one user.

Here are the capabilities of the server: ----IMAP RESPONSE----

  • OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE NAMESPACE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
    ----IMAP REQUEST----
    aaab LOGIN “bob”
    ----IMAP RESPONSE----
    aaab OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS BINARY MOVE SNIPPET=FUZZY PREVIEW=FUZZY PREVIEW STATUS=SIZE SAVEDATE NAMESPACE LITERAL+ NOTIFY SPECIAL-USE COMPRESS=DEFLATE QUOTA] Logged in

That’s a super standard server.

Does it show up in webmail, if that’s available? What about a different mail client?