When I try to send a e-mail from Read User Mail, amavis is saying to me:
INVALID HEADER: INVALID 8-BIT CHARACTERS IN HEADER
Non-encoded 8-bit data (char E1 hex): Date: s\341b, 26 jul 2008 [...]
X-Mailer: Webmin 1.410
WHAT IS AN INVALID CHARACTER IN MAIL HEADER?
The RFC 2822 standard specifies rules for forming internet messages. It does not allow the use of characters with codes above 127 to be used directly (non-encoded) in mail header.
If such characters (e.g. with diacritics) from ISO Latin or other alphabets need to be included in a header, these characters need to be properly encoded according to RFC 2047. Such encoding is often done transparently by mail reader (MUA), but if automatic encoding is not available (e.g. by some older MUA) it is a user's responsibility to avoid using such characters in mail header, or to encode them manually. Typically the offending header fields in this category are 'Subject', 'Organization', and comment fields in e-mail addresses of 'From', 'To' or 'Cc' header fields.
Sometimes such invalid header fields are inserted automatically by some MUA, MTA, content checker, or other mail handling service. If this is the case, that service needs to be fixed or properly configured. Typically the offending header fields in this category
are 'Date', 'Received', 'X-Mailer', 'X-Priority', 'X-Scanned', etc.
If you don't know how to fix or avoid the problem, please report it to _your_ postmaster or system manager.
Received: by apaair.aero (Postfix, from userid 0)
id 0DC091A42DE; Sat, 26 Jul 2008 09:37:13 +0200 (CEST)
X-Mailer: Webmin 1.410
Date: sáb, 26 jul 2008 09:37:13 +0200 (CEST)
As you can see, Date field shows "sáb".
Webmin is configured in English (I have tested it with several configurations of my user interface (mainly English and Spanish). My Operative System is Mandriva 2008.1, and it's configured in Spanish.
This problem also occurs when I try to use some words with special characters in Spanish, as "España" or "avión" into Subject field.
Change codifications of 'Date', 'Received', 'X-Mailer', 'X-Priority', 'X-Scanned', 'Subject', 'Organization', 'From', 'To', 'Subject' or 'Cc' header fields to meet other languages codifications, according to RFC 2047.
Usermin mail module also have this problem (not with the date field because date is used in English), for example, when I try to use some Spanish characters into my Subject field.