[exim] server for Gmail problem: NULL character(s) present

I've followed the instructions for getting set up so I can use my
exim4 (4.69 on Debian) server to send mail from my Gmail account, but
when I try to connect from google I get

2010-11-20 15:19:19 [15973] SMTP connection from [209.85.215.44]:39470
I=[64.15.147.59]:25 (TCP/IP connection count = 1)
2010-11-20 15:19:20 [16070] SMTP syntax error in
"\200(\001\003\001?\017???\020??\004\001?\200??\005??"
H=mail-ew0-f44.google.com [209.85.215.44]:39470 I=[64.15.147.59]:25
NULL character(s) present (shown as '?')
2010-11-20 15:19:20 [16070] SMTP connection from
mail-ew0-f44.google.com [209.85.215.44]:39470 I=[64.15.147.59]:25 lost
(error: Connection reset by peer)
2010-11-20 15:19:20 [16070] no MAIL in SMTP connection from
mail-ew0-f44.google.com [209.85.215.44]:39470 I=[64.15.147.59]:25 D=1s

but

swaks -a -tls -q AUTH -s markup.co.uk -p 25 -au xx -ap yy

works

What am I doing wrong?

Thanks,

ht
-- 
            Henry S. Thompson, Markup Systems Ltd.
               Cavers Garden Farm, Denholm; by Hawick; TD9 8LN
                            +44 (0) 7866 471 388
           Fax: (44) 131 651-1426, e-mail: ht@???
            URL: http://www.markup.co.uk/
[mail really from me _always_ has this .sig -- mail without it is forged spam]