Issues - Sunbird Lightning Calendar
From MozillaZine Knowledge Base
Alerts by email are not sent (SB0.2, MozCal on FF)
Issue: Email alerts are not sent by Sunbird 0.2, nor by Calendar Extension on Firefox.
Background: Sunbird 0.2 is built on a plain Mozilla application core. The Calendar extension builds on the core application to which it is added (Firefox, Thunderbird, or Mozilla Suite). Some network services are not available in some combinations. See Calendar vs. Sunbird. (Reported: bug 237148.)
Workarounds: Instead, use Calendar Extension on Thunderbird or on Mozilla Suite.