[MlMt] Tags in r5460

[Bill Cole]

On 5 Mar 2018, at 11:35, Benny Kjær Nielsen wrote:

> MailMate has an auto-create feature to easily create new tags (which 
> is triggered when entering an unknown tag name). It shows a 
> “warning” sheet the first time which can then be suppressed if the 
> user tells it to do so.

It may be informative to look at the formal syntax definition for IMAP 
at https://tools.ietf.org/html/rfc3501#section-9 and especially take 
note of these snippets:

         (1) Except as noted otherwise, all alphabetic characters
         are case-insensitive.  The use of upper or lower case
         characters to define token strings is for editorial clarity
         only.  Implementations MUST accept these strings in a
         case-insensitive fashion.

[...]
     atom            = 1*ATOM-CHAR

     ATOM-CHAR       = <any CHAR except atom-specials>

     atom-specials   = "(" / ")" / "{" / SP / CTL / list-wildcards /
                   quoted-specials / resp-specials

     flag            = "\Answered" / "\Flagged" / "\Deleted" /
                   "\Seen" / "\Draft" / flag-keyword / flag-extension
                     ; Does not include "\Recent"

     flag-keyword    = atom


I believe this means that IMAP keywords are case-insensitive. Thus if 
you have 2 MM Tags that differ only in case and they are mapped to IMAP 
keywords that differ only in case, you could run into trouble if you try 
to use both in one IMAP mailbox. The behavior of a server when told to 
create a new keyword differing only in case from an existing keyword in 
a particular mailbox is undefined.