## Summary
`ImapGetAllFoldersService.isMailboxSelectable` checked
`mailbox.flags?.has('\\Noselect')`, which is case-sensitive. Per [RFC
3501 §6.3.8](https://www.rfc-editor.org/rfc/rfc3501#section-6.3.8), IMAP
attribute names are case-insensitive — different servers spell the flag
differently:
| Server | Spelling |
|---|---|
| Dovecot | `\Noselect` |
| Stalwart | `\NoSelect` |
| Cyrus | `\Noselect` |
| RFC examples | `\NOSELECT` |
The previous check only caught Dovecot's spelling. On other servers,
virtual namespace placeholders (e.g. Stalwart's `Shared Folders` parent)
passed through `isMailboxSelectable` and got persisted as folders. When
`MessagingMessageListFetchJob` later ran, it issued `SELECT "Shared
Folders"`, the server correctly rejected it with `NO [NONEXISTENT]
Mailbox does not exist.`, and the entire message-list fetch failed for
the channel.
## Reproduction
1. Connect an IMAP account whose server advertises a `\NoSelect` (or
`\NOSELECT`) namespace placeholder. Stalwart Mail v0.15.x exhibits this
with shared mailboxes:
```
* LIST (\NoSelect) "/" "Shared Folders"
```
2. The folder discovery job persists it as a syncable folder.
3. `MessagingMessageListFetchJob` runs and fails:
```
IMAP: Error fetching message list: D0 SELECT "Shared Folders"
responseStatus: NO serverResponseCode: NONEXISTENT
```
## Fix
Iterate the flag set and lowercase-compare against `'\\noselect'`. This
matches every legal spelling without changing behavior for compliant
`\Noselect` clients.
```diff
private isMailboxSelectable(mailbox: ListResponse): boolean {
- return !mailbox.flags?.has('\\Noselect');
+ if (!mailbox.flags) return true;
+ for (const flag of mailbox.flags) {
+ if (flag.toLowerCase() === '\\noselect') return false;
+ }
+ return true;
}
```
## Test plan
- [x] Existing `\Noselect` test cases (`should not issue STATUS against
a \Noselect folder`, parent-reference preservation, Sent-folder
exclusion) still pass — the lowercase comparison subsumes them.
- [x] New parameterized test covers `\Noselect`, `\NoSelect`,
`\NOSELECT`, `\noselect` spellings against a Stalwart-style `Shared
Folders` namespace placeholder, asserting Twenty does **not** issue
`STATUS` on the placeholder and does **not** include it in the
discovered folder set.
---------
Co-authored-by: neo773 <62795688+neo773@users.noreply.github.com>
