Hi!

Some (considerable) time ago, I, as one of the Mailspring (https://getmailspring.com/) users, had a problem with setting up IMAP email account hosted on home.pl. I was able to narrow down the problem to how the Mailspring handles server response regarding folder list. The problem is twofold: a) how the response is handled by Mailspring's IMAP libraries, b) how the server itself responds. As to the first part of the problem I submitted relevant bug reports (https://github.com/MailCore/mailcore2/issues/1908 and https://github.com/dinhvh/libetpan/issues/403) and but the second part appears to belong here, since home.pl uses Dovecot as their IMAP server.

Now about the problem.

When XLIST is used to get the list of the folders, I get, for example:

3 XLIST "" "*"

• XLIST (\HasNoChildren \) "." "Archive"
• XLIST (\HasNoChildren \) "." "Courses"
• XLIST (\HasNoChildren \Draft) "." "DRAFTS"
• XLIST (\HasNoChildren \Inbox) "." "INBOX"
• XLIST (\HasChildren \) "." "PhD"
• XLIST (\HasNoChildren \) "." "PhD.Advisor"
• XLIST (\HasNoChildren \) "." "PhD.Archive"
• XLIST (\HasNoChildren \) "." "PhD.Articles"
• XLIST (\HasNoChildren \) "." "PhD.Conferences"
• XLIST (\HasNoChildren \) "." "PhD.Journals"
• XLIST (\HasNoChildren \) "." "PhD.Thesis" 3 OK Completed

Compare this with the LIST output:

4 LIST "" "*"

• LIST (\HasNoChildren) "." "Archive"
• LIST (\HasNoChildren) "." "Courses"
• LIST (\HasNoChildren \Drafts) "." "DRAFTS"
• LIST (\HasNoChildren) "." "INBOX"
• LIST (\HasChildren) "." "PhD"
• LIST (\HasNoChildren) "." "PhD.Advisor"
• LIST (\HasNoChildren) "." "PhD.Archive"
• LIST (\HasNoChildren) "." "PhD.Articles"
• LIST (\HasNoChildren) "." "PhD.Conferences"
• LIST (\HasNoChildren) "." "PhD.Journals"
• LIST (\HasNoChildren) "." "PhD.Thesis" 4 OK Completed

Notice, how in the XLIST example, every item has an additional “empty” flag (“\”). This part causes libetpan to fail. While ignoring the problem as a library's problem would be perfectly understandable, I think it should be also considered if something shouldn't be done on Dovecot's end. Granted, XLIST has been long depreceated, however it still is implemented and it should be implemented properly. Perhaps I'm mistaken, but I failed to find any mention of a thing like “empty flag”. It might not be prohibited, but it strikes me as something bizarre.

I am unable to get the information about the Dovecot version used by home.pl, but I suspect this problem may still be present up to the newest version. Also, if someone is willing to take a closer look at the problem, I can provide you with an email account for testing purposes.

Best regards! Bogdan