Am 07.09.2017 um 20:07 schrieb hw: > Gordon Messmer wrote: >> On 09/07/2017 08:11 AM, Stephen John Smoogen wrote: >>> This was always >>> problematic because DNS hostnames and email addresses in the RFC >>> standards were case insensitive >> >> >> Not quite. SMTP is required to treat the "local-part" of the RCPT >> argument as case-sensitive, and to preserve case when relaying mail. >> The destination is allowed to treat addresses according to local >> policy, but in general SMTP is case sensitive with regard to the user >> identifier. > > Last time I checked, RFCs said that local parts *should not* be case > sensitive, > and cyrus defaulted to treat them case sensitive, which is a default > that usually > needs to be changed because senders of messages tend to not pay any > attention to > the case sensitiveness of recipient addresses at all, which then > confuses them like > any other error. The relevant part from the RFC: https://www.ietf.org/rfc/rfc5321.txt 2.4. General Syntax Principles and Transaction Model 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. Alexander