Header too Large Error
From Roaring Penguin
To fix this you can increase the maximum size.
1. Edit the file /etc/mail/sendmail.mc and make changes here ONLY.
2. In the section containing the define('conf... lines add the line
define(`confMAX_HEADERS_LENGTH', 262144)dnl
3. Then create the actual Sendmail configuration file
etc/mail/sendmail.cf:
make -C /etc/mail
4. Load the changes into Sendmail:
/etc/init.d/sendmail reload