lowercase senderaddress

Hugo van der Kooij hvdkooij at vanderkooij.org
Tue Oct 27 21:06:34 GMT 2009

On 10/27/09 17:29, Oli Schacher wrote:
> Hi list,
> Apparently, sender and recipient address are changed to lowercase
> characters in MailScanner(with postfix).  This seems to break BATV if
> the sender address contains uppercase characters and leads to rejected
> mails if the receiving MTA does sender address verification ( I know it
> shouldn't, but I can't do anything about that).

RFC 5321 clearly indicates that the local part should be considered case 

    Verbs and argument values (e.g., "TO:" or "to:" in the RCPT command
    and extension name keywords) are not case sensitive, with the sole
    exception in this specification of a mailbox local-part (SMTP
    Extensions may explicitly specify case-sensitive elements).  That is,
    a command verb, an argument value other than a mailbox local-part,
    and free form text MAY be encoded in upper case, lower case, or any
    mixture of upper and lower case with no impact on its meaning.  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.  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.  Mailbox domains follow normal DNS rules and are
    hence not case sensitive

It is not recommended to rely on it but mangling it is in violation of 
the MUST statement in this RFC.


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