You should enable mail queue if number of emails will send from your Niche Social Network site is over email sending limits of your hosting server. Here is how to configure:
1. Go to System admin -> Mails -> Mail settings tab -> Select "Yes, enable email queue" at Email Queue field.
2. Enter appropriate value into "Mail Count" field. Mail count is number of emails will send out from your site every 1 minute (you can change this time interval by changing "Background Mailer" cron job at System admin -> Tasks -> manage settings. If you're not sure how to change it, please keep it default 1 minute. )
Ex: your hosting email sending limits per hour is 1500 emails (contact your hosting provider to know get this number)
Number of emails can send max per minute will be: 1500/60 = 25 emails
--> Value for "Email count" will be 25 in this case.
Importance: if you enable email queue, email sending will be delayed as all emails will be added into queue first then send later.