Sorry Aki, you are right. 

On Sat, Sep 29, 2018 at 09:59, Aki Tuomi <aki.tuomi@open-xchange.com> wrote:
> On 29 September 2018 at 10:05 Rupert Gallagher <ruga@protonmail.com> wrote:
>
>
> +1
>
> A similar problem occurs with "."
>
> Sent from ProtonMail Mobile
>
> On Fri, Sep 28, 2018 at 15:44, Wojciech Puchar <wojtek@puchar.net> wrote:
>
> > user attempts to create folders with /
> > dovecot naturally cannot create it so it returns error but outlook of
> > course "create" it and keep data in local store only. data is lost when
> > you remove local store .pst file.
> >
> > The question is - can dovecot be configured so it will automatically
> > replace slash in name with something else?

And how would this help? Outlook would still go ahead and create the folder with / in it, and dovecot would create a folder with, say - in it and now you'd have two folders.

Aki