exim4 fetchmail delivery more than 10 rejected

[Harry Putnam <reader@newsguy.com>]

An exim4 default of accepting no more than 10 messages at one time
when I use fetchmail to download pop3 mail.

"no immediate delivery: more than 10 messages received in one
connection"

Shows up in the mail.log and anything over 10 is stuck in a que and
delived later.

I want to set that limit to a higher number, but googling on that
produces a bewildering array of different ideas about how to do that.

I've tried adding this line:

 smtp_accept_queue_per_connection=300

To /etc/exim4/exim4.conf.template which causes a failure when I run 
   /etc/init.d/exim4 reload
(It generates a new conf that exim4 does not accept.

Then I tried adding it to:
  /etc/exim4/update-exim4.conf.conf

But got the same result.
I tried using no spaces between equal sign and value.
And using spaces before and after.

   smtp_accept_queue_per_connection=300
    smtp_accept_queue_per_connection = 300

Didn't seem to matter.  Still produces a non-usable config.

So, does anyone know how I might change the default value of 10 msgs
per connection to some higher number?

The exim4 FAQ tells of a way to put the load on fetchmail and diddle
around with its config, but  also says one might change it in exim4 but
is not clear about where this change is made.