Creating subfolders with dovecot

I have a dovecot IMAP server on which all of my e-mail is stored. If I create a new folder on the server with eM client, the server creates an mbox file. Dovecot then responds with “mailbox doesn’t allow inferior mailboxes” if I try to create subfolders of the first folder (since the mbox file doesn’t support this.)

Some other e-mail clients (e.g. Sylpheed) allow me to create a folder with subfolders by adding a trailing slash to the folder name. On the server side, this results in a directory being created instead of an mbox file. E.g. I can create a folder “2016/” that corresponds to directory on the server containing mbox files “jan”, “feb”, etc. But eM complains that the “/” is an unsupported character and refuses to create the folder.

Is there any way to have eM tell dovecot that I want to create a folder with subfolders, instead of a plain folder?

Nick S.

Hello Nick,
if your server doesn’t support subfolders, eM Client can’t make one for you.
Are the already existing subfolders synchronizing as correctly to eM Client though?


Hi Olivia. Sorry is has taken me so long to get back to you, I must have missed your reply.

The server does support sub-folders - Sylpheed can create them, and eM Client can navigate the sub-folders that already exist on the server. The problem is that eM Client objects to appending a slash to the name of a new folder, which is how dovecot understands that the new folder is supposed to contain sub-folders. So I can create a sub-folder of something that has already been created (with Sylpheed), but I cannot create a new folder that will itself contain folders.

The technical reason behind this is that the server represents folders containing sub-folders as directories on disk, while the folders containing mail are files. So the server needs to know whether it should create a directory or a file when I create a new folder. I can tell it to create a directory by appending a slash to the name, but this is not allowed in eM.

Nick S.