[Dovecot] ssl cert for mail server

[cc "maco" young]

for testing a new ssl cert.  it works ok for browsers, but

>  openssl s_client -crlf -connect ms1.trailsandtribulations.net:443

=> verify error:num=19:self signed certificate in certificate chain

is this ssl cert - as it's constructed - is ok for mail clients?  (realize
needs to be on mail port etc - right now talking about the cert itself.)
 have had problems with thunderbird, and was wondering if this might be
part of the problem.