Scenario
You have been testing and want to drop all accumulated notifications.
Method
Uninstall the EMQ addon, drop the EMQ tables, reinstall the EMQ addon. This can be done live, as no other entity will be using those tables.
EMQ stores all data in Active Objects database tables. The Prefix for this is AO_2B6685, some example Table names are:
AO_2B6685_AUDIT_DIGEST_HISTORY AO_2B6685_AUDIT_EMAIL AO_2B6685_AUDIT_EMAIL_ISSKEY AO_2B6685_AUDIT_LOG AO_2B6685_AUDIT_EMAIL_RECIP ...
A low level db tool can be used drop drop the tables. For Postgres databases, selecting all AO_2B6685 tables and using right-click > Drop-Cascaded will do the job.