Opening email relay still requires encrypted SSL?

[albatroz]

I am planning to open relay for an app server so it can send emails through my
Zentyal email server. In this case, will I still need to use TLS encryption?

It happens that as I am not using a signed certificates some applications get
broken and I finish with an error like this on the Postfix log file
Nov 17 11:49:03 mail postfix/smtpd[10244]: lost connection after STARTTLS from u
nknown[172.19.39.11]

Ref: http://doc.zentyal.org/en/mail.html

[christian]

1 - no it doesn't require any certificate
2 - for application running "inside" (meaning on your Intranet), it is not "open relay"