Checking voicemail from out side line

how would I check my voice mail from an outside line?

We use a standard extension macro for incoming calls. We have it set up so if someone presses the * key, they are redirected to voicemail.

exten => s,1,Noop(${MACRO_CONTEXT})
exten => s,2,Dial(SIP/${MACRO_EXTEN},15,rtT)
exten => s,3,Voicemail(${MACRO_EXTEN}@${MACRO_CONTEXT},us)
exten => s,103,Voicemail(${MACRO_EXTEN}@${MACRO_CONTEXT},bs)
exten => s,104,Hangup
exten => a,1,VoicemailMain(${MACRO_EXTEN}@${MACRO_CONTEXT})
exten => a,n,Hangup()