[Pkg-exim4-users] send from MUA fails

[Hal]

I've just replaced a working exim3 install with exim4 and mail sent  
from Mac's mail.app always fails whether the mac is on the same net  
as the mail server or on a remote machine.  This setup was working  
under exim3.  The exim4 config was set up from scratch using debian  
conf utilities and then I added a router for a virtual domain I  
handle.  Incoming mail from smtp servers on the internet always  
works.  Sending from the command line on the server works.  But,  
sending from the mail.app MUA always ends with the following in debug  
output (all the clients are OS X so no other MUA has been tried).

5605 SMTP<< EHLO [10.0.1.14]
5605 sender_fullhost = dsl081-064-038.sfo1.dsl.speakeasy.net  
([10.0.1.14]) [64.81.64.38]
5605 sender_rcvhost = dsl081-064-038.sfo1.dsl.speakeasy.net  
([64.81.64.38] helo=[10.0.1.14])
5605 set_process_info:  5605 handling incoming connection from  
dsl081-064-038.sfo1.dsl.speakeasy.net ([10.0.1.14]) [64.81.64.38]
5605 host in pipelining_advertise_hosts? yes (matched "*")
5605 host in auth_advertise_hosts? yes (matched "*")
5605 host in tls_advertise_hosts? no (option unset)
5605 SMTP>> 250-teak.retrotech.org Hello  
dsl081-064-038.sfo1.dsl.speakeasy.net [64.81.64.38]
5605 250-SIZE 52428800
5605 250-PIPELINING
5605 250 HELP
5605 SMTP>> 421 teak.retrotech.org lost input connection
5605 LOG: smtp_connection MAIN
5605   SMTP connection from dsl081-064-038.sfo1.dsl.speakeasy.net  
([10.0.1.14]) [64.81.64.38] lost

No further explanation for the "SMTP>>421" can be found with -d+all!   
421 is service not available, but no idea why.

An suggestions?  I've been reading but can't find any leads.

Note the virtual domain is not directly involved as sending is from  
the real domain name.

Thanks.