I don’t know how the backend works in the finest detail, but the email_time_window_mins is just a delay setting before the first email goes out. During this time, any user that is set to receive the email may “forfeit” the email if they happen to be active within the window of period (official terminology: email skipped; skip reasoning: User was seen recently).
The default delay is 10 minutes, meaning the post must be live for 10 minutes, and only then will the emails be sent.
Richie’s issue is the time difference between the first email and the last email… a delay of one hour. This is probably due to the sheer amount of emails that need to be sent, though I cannot say for certain either.
Changing the setting above would only expedite the sending of the first email, but not address the completion duration of the entire batch of 22,000 emails.
What would be the recommended setting, obviously dependent on infrastructure capability?
Could a high setting result in server issues in terms of load or other?