After upgrade I was unable se to send mails through my sendmail, from both OSX 10.10.4 and upgraded iOS9 …

this was in my sendmail log:

Jul 12 19:58:03 orin sendmail[12164]: STARTTLS=server, error: accept failed=0, SSL_error=1, errno=0, retry=-1
Jul 12 19:58:03 orin sendmail[12164]: STARTTLS=server: 12164:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handsh
ake failure:s3_pkt.c:1053:SSL alert number 40

fix is amazingly easy and effective:

generate dh2048 certificate:

openssl gendh -out dh_2048.pem -2 2048

and add to sendmail.mc:

define(`confDH_PARAMETERS',`/etc/mail/certs/dh_2048.pem')

then recompile your .mc and restart sendmail.