Voicemail email not sending notification

Good day,

We enable voicemail on an extension and set email address,before it was sending notification, but lately its not sending anymore notifications.

deferred
[email protected]

FreePBX 2.8.0.3
Asterisk 1.4.21.2

Did you look at where the email is routing through?
In other words are you sending your email through an internal mail server?
Has that IP changed? have rules been added to that server for smtp auth and such.
My guess is your no longer allowing those messages to relay from your PBX.