[Users] Address book defaults to lower case

blind Pete peter_s_d at fastmail.com.au
Mon Apr 3 07:20:13 CEST 2017

On Wed, 22 Mar 2017 14:34:13 +0000
Dave Howorth <dave at howorth.org.uk> wrote:

> On Wed, 22 Mar 2017 11:55:35 +0100
> Andrej Kacian <andrej at kacian.sk> wrote:
> > On Wed, 22 Mar 2017 10:11:25 +0000
> > Brian Morrison <bdm at fenrir.org.uk> wrote:
> > 
> > > On Wed, 22 Mar 2017 10:34:06 +0100
> > > wwp wrote:
> > > 
> > > > I can't believe a server wants capitalized names in email
> > > > addresses (or case sensitiveness in general). Would you show us
> > > > the error thrown by this server?
> > > 
> > > Actually folks, the local part of the address before the @ should
> > > have case preserved, there are people who do use capitalized
> > > addresses in this way.
> > > 
> > 
> > You are both correct and incorrect (as is frequently the case with
> > RFCs).
> > 
> > RFC 2821[1] manages to contradict itself. In section 2.4, it says:
> > 
> >    [...] The local-part of a mailbox
> >    MUST BE treated as case sensitive.  Therefore, SMTP
> > implementations MUST take care to preserve the case of mailbox
> > local-parts. Mailbox domains are not case sensitive.  In
> > particular, for some hosts the user "smith" is different from the
> > user "Smith".  However, exploiting the case sensitivity of mailbox
> > local-parts impedes interoperability and is discouraged.
> > 
> > Then later, in section 4.1.2:
> > 
> >    While the above definition for Local-part is relatively
> > permissive, for maximum interoperability, a host that expects to
> > receive mail SHOULD avoid defining mailboxes where the Local-part
> > requires (or uses) the Quoted-string form or where the Local-part
> > is case- sensitive.
> > 
> > Arguably, "MUST" takes precedence over "SHOULD".

No argument about it.  Read section 2.3 Terminology.  

Background: For many years I have been annoyed by technical documents
that devote large sections to defining the obvious.  What happened was
that a couple of centuries ago the British parliament defined many of
these little terms and their interpretation in "new" laws - but this
happened after the American revolution (also known as the war of
independence).  So, what is actually a difference of dialect was
prompting me to ask, "What is wrong with these people, didn't they go
to school?".  

Much like Boolean algebra uses OR and XOR as two similar words that do
similar but different things because it is the least ugly way to do
what must be done, the Standards bodies have landed on the British
standard usage because they need a standard and the British one

> But in particular, the part in 2.4 does apply to claws, does it not?
> In terms of the address book, it must treat the local part as
> case-sensitive.
> Of course it can also comply with 4.1.2 in terms of mailboxes that it
> defines. The two sections are not contradictory.
> Or have I misunderstood something?

You are pretty much on the money.  

Restating the RFC; case sensitive local parts are a bad thing, don't do
it, but if you encounter an email from an idiot be polite play along
and respect it.  

As an edge case, "JohnSmith" is easier to read than "johnsmith" or
"JOHNSMITH" and I would use it as a readability aid, but I would expect
all capitalization variants to refer to the one user - even though it
is theoretically possible that there are 2**9 different John Smiths

> > 1. https://tools.ietf.org/html/rfc2821

Not respecting capitalization, in the local part, is a bug not a

Sorry for the English lecture, but I am working off a few decades of

> > Regards,


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