headers too large (32768 max)

Problem

When I submit a message locally, it dies with: headers too large (32768 max) from local during message collect

Solution

Don't send bulk mail. Break it up into multiple messages with smaller recipient lists.

But if you really have to, edit /etc/mail/submit.cf and edit the section:

# Maximum length of the sum of all headers
#O MaxHeadersLength=32768
O MaxHeadersLength=256000