This was a ridiculous miss, where on first time installation, the
well designed default e-mail template was never installed in the
DB! I never spotted this because my local dev setup, and
surprisingly, nobody ever complained that the default campaign
template was a blank slate with no styles.
Certain SMTP hosts limit the total number of messages that can be
sent within a window, for instance, X / 24 hours. The concurrency
and message rate controls can only limit that to a max of
1 messages / second, without a global cap.
This commit introduces a simple sliding window rate limit feature
that counts the number of messages sent in a specific window, and
upon reaching that limit, waits for the window to reset before
any more messages are pushed out globally across any number of
campaigns.
Context: https://github.com/knadh/listmonk/issues/119
Kailash Nadh