More special chars in mailbox names

David Carter dpc22 at
Wed Oct 1 05:03:12 EDT 2008

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 
> ! # $ & ' ; < > ? [ ^ ` } |

We have used:

  "\\\" #$%'()*+,-.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 

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
University Computing Service,            Phone: (01223) 334502
New Museums Site, Pembroke Street,       Fax:   (01223) 334679
Cambridge UK. CB2 3QH.

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