I am using a dovecot imap server, and am trying to add a sub-directory under my email. I have a folder name saved and would like to add more folders under it.

Anyway, when I do try and add a new folder, I get the error "Server does not allow inferiror mailboxes". How can I change this option? I checked the entire etc/dovecot.conf file.

Thanks for your help.

what kind of folder are you trying to add? how are you trying to add it? afaik dovecot is only for maildir folders, and so you'd either create them through dovecot, i.e. in your mail client, or use a tool to create full maildir layouts. in reality this is quite simple:but there are futher extensions onto the maildir format for all sorts of things which i can't remember. courier has a built in utility called maildirmake to create the structure for you

I was just trying to add it through my mail client. I have tried Thunderbird and Outlook. I am able to add a folder under the main folder, but not under that

I had the same problem from Outlook.
I found that dovecot supports two mail directory layout standards.
One is mbox, a simple one that doesn't let you have sub-folders, and Maildir, which does.
dovecot tries to guess which you want, based on its system configuration file, and by default gave me mbox.
I found I could make it use Maildir by removing the directory 'mail' from below my home directory and creating one called 'Maildir' instead. Then when I went back in with Outlook I was able to create a hierarchy of folders and it worked fine.
Hope this helps.
Peter

Thanks. I'll try it out when I have some time, however, now it is not a priority.