[exim] sending e-mail through a directnic server

This has been working for over 4 years but it just stopped after
DirectNIC changed their servers. In theory, all I needed to do was
reconfigure exim4.conf by running
  # dpkg-reconfigure exim4-config
and putting in the new server name. Then I update passwd.client to use
the new server name. The account credentials stay the same.

Indeed, all the Thunderbird clients in the office just needed the new
server name. As an aside, Thunderbird doesn't seem to think there is
anything special about the setup - ssl/tls encryption using port 465 for
sending.

 # openssl s_client -connect mail.rossland.dental:465

also seems to indicate that the connection works just fine. I can log
in, create a message and send it - but it only goes to the "rcpt to:",
not to anyone I put in the "to:" data. Here's the dialog section dealing
with creating the message:

mail from: sendmail@???
250 OK
rcpt to: sendmail@???
250 Accepted
data
354 Enter message, ending with "." on a line by itself
from: sendmail@???
to: gary@???, garydale@???
Date: 26 Nov 2019 20:59:00 -0500
subject: test message from s_client with 2 recipients
another test message - with a date possibly.
.
250 OK id=1iZmbP-005vB9-E0
DONE

The mail doesn't get to either "to:" address but does show up in the
"rcpt to:" inbox.


From the above, I gather that I have the correct names, ports and
credentials. However I'm not able to send mail. It just sits in my
server's mailq.


Here's my update-exim4.conf.conf file.

dc_eximconfig_configtype='smarthost'
dc_other_hostnames='molar.rossland.dental'
dc_local_interfaces='127.0.0.1 ; ::1'
dc_readhost=''
dc_relay_domains=''
dc_minimaldns='false'
dc_relay_nets=''
dc_smarthost='mail.rossland.dental::465'
CFILEMODE='644'
dc_use_split_config='false'
dc_hide_mailname='false'
dc_mailname_in_oh='true'
dc_localdelivery='mail_spool'

Any ideas?