Adding to the email header of the line:

Content-Type: text/plain; charset="UTF-8"

Allows to the mail-cilent to define the letter encoding automaticly.
It provides an ability of reading of the text by the language another from the englisn.

PATCH:
— src/libs/zbxemail/email.c 2008-07-17 12:28:32.000000000 +0300
+++ src/libs/zbxemail/email.c 2008-07-17 12:28:32.000000000 +0300
@@ -230,7 +230,7 @@
time(&email_time);
local_time = localtime(&email_time);
strftime( str_time, MAX_STRING_LEN, "%a, %d %b %Y %H:%M:%S %z", local_time );

• cp = zbx_dsprintf(cp,"From:<%s>\r\nTo:<%s>\r\nDate: %s\r\nSubject: %s\r\n\r\n%s",smtp_email,mailto,str_time,mailsubject, mailbody);
  + cp = zbx_dsprintf(cp,"From:<%s>\r\nTo:<%s>\r\nDate: %s\r\nSubject: %s\r\nContent-Type: text/plain; charset=\"UTF-8\"\r\n\r\n%s",smtp_email,mailto,str_time,mailsubject, mailbody);
  e=write(s.socket,cp,strlen(cp));
  zbx_free(cp);
  zbx_free(mailsubject);