I am new to OpenBSD and smtpd, please ignore if this is too trivial to inform. Smtpd checks for two files instead of one when no certificate name is specified for "listen on". Though one of the examples shows exactly what has to be done, I thought it helps mentioning explicitly.
Index: smtpd.conf.5 =================================================================== RCS file: /cvs/src/usr.sbin/smtpd/smtpd.conf.5,v retrieving revision 1.36 diff -u -r1.36 smtpd.conf.5 --- smtpd.conf.5 29 Oct 2010 09:16:08 -0000 1.36 +++ smtpd.conf.5 16 Dec 2010 22:53:51 -0000 @@ -116,9 +116,9 @@ .Ar name is specified, the .Pa /etc/mail/certs -directory is searched for a file named by joining -the interface name with a .crt extension, e.g.\& -.Pa /etc/mail/certs/fxp0.crt . +directory is searched for files named by joining +the interface name with .crt, .key extensions, e.g.\& +.Pa /etc/mail/certs/fxp0.crt /etc/mail/certs/fxp0.key . .Pp If the .Ic enable auth
