sendmail configuration

I am trying to make sure my mail server is secure. I belive I already enabled pop3s and imaps so that it uses SSL, and therefore encrypting user passwords.

I can also do the same thing with sendmail when I want to send mail from my mailserver.

However, I need to have outside domains be able to access sendmail to relay to me, right? I unfortunately get this error when I try to send mail from a different account to my mail server:

Relaying denied. Proper authentication required.)

Is there something that I need to allow other domains to send mail to me without authenticating?

I think these are the important settings I have in my sendmail.mc file.

define(`confAUTH_OPTIONS', `A')dnl

TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl

define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl

DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

Any help is appreciated, thanks