Add some info about helpful indexes
Add some info about helpful indexes

Signed-off-by: Dan McGee <a6e5737275ff1276377ee261739f3ee963671241@gmail.com>

zyegfryed/django-mailer,mudiarto/django-mailer,PolicyStat/django-mailer,filterfoundry/django-mailer,toofishes/django-mailer,PolicyStat/django-mailer