mjr is partially correct about the allowed format, and completely 
correct about the fact that the e-mail address provided is incorrect.

mjr is correct that this e-mail address is not an RFC 822 compliant 
address.  However, RFC 822 is deprecated - RFC 5322 is controlling 
now.  The ABNF for the local part is:

local-part      =   dot-atom / quoted-string / obs-local-part

For purposes of this example, dot-atom and obs-local-part (which is 
the RFC 822 definition of local-part) are the same.  There must be at 
least 1 non-dot character before the '@' part of the e-mail address.   
So the e-mail address provided is correctly identified as invalid.

FYI: this would be the correct way to represent that address:

"c.p.c."@something.com

I'm almost positive that this is NOT a valid rfc822 compliant email address:

The spec states that the local-part is:

local-part  =  word *("." word)             ; uninterpreted
                                                          ; case-preserved

Where a word is an ATOM or QUOTED STRING. An ATOM is a string of ASCII 
characters EXCEPT ()<>@,;:\".[].  The *("." word) part indicates that 
one or more occurrences of a period FOLLOWED by a word are compliant. 
In other words, the local-part cannot end with a period.

Hi,

turba thinks the following working e-mail address is invalid:

c.p.c.@something.com

Quick testing shows it's the last dot before the @ char
that's triggering the syntax check.

Thomas