More special chars in mailbox names

[David Carter]

On Tue, 30 Sep 2008, Ken Murchison wrote:

> I started wondering what other special characters we might want to allow. 
> The original authors were more restrictive with GOODCHARS than the RFC. 
> AFAICT the following characters are permitted by RFC 3501 but aren't included 
> in GOODCHARS
>
> ! # $ & ' ; < > ? [ ^ ` } |

We have used:

#define GOODCHARS
  "\\\" #$%'()*+,-.0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ"[]_`abcdefghijklmnopqrstuvwxyz{|}~"

for a number of years now without any obvious problems. This list was 
taken from someone's suggestion on info-cyrus at the time.

For what it is worth, UW imapd allows '%' and '*' in mailbox names, which 
is why they are on the list above. Those are the two characters I am most 
dubious about. Hardly anyone uses '%'. '*' seems quite popular as a trick 
to push mailboxes up to the top of an alphabetically sorted list.

> ! and ^ have special meaning to Cyrus, so we may not want to add these to 
> GOODCHARS.

I had to remove '!' from the list above when we moved from 2.1.x.

> & and ? might conflict with modified UTF-7 encoding.

& shouldn't be allowed without checking for a valid modified UTF-7 
sequence. What is the problem with '?'.

-- 
David Carter                             Email: David.Carter at ucs.cam.ac.uk
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