Newsletter Sending Frequency is nothing but the engine speed to measure the emails per hour to deliver emails to your subscriber.
Cron is the schedule time allocated to send newsletter/email provided by the SMTP. Get more details about Cron in this Wikipedia Article.
In order to choose the Newsletter Sending Frequency the following things are to be in consider,
- It depends upon what sending method are you using i.e. whether from WordPress or from Third Party (SMTP)
- Limitations of sending emai
- Speed of your server
Read this article about Sending Newsletter/email.
Limitations of sending email
Limitations of sending email are decided by your hosting company or third party (SMTP). They decide how much emails can send for the day or hour by you to your subscriber.
Ultimate Newsletter cannot detect the frequency decided by your hosting company.
Speed of your Server
Sending Frequency and cron is also depends upon your server speed. If your server is fast then it is well good.
Ultimate Newsletter generally takes to send each emails every one seconds to the subscribers. Let us discuses with the example.
If wanted to send 100 emails to your subscribers. Assume cron set by your host company is 70 newsletter/emails every 1 hour. Ultimate Newsletter make a queue of emails in batches and send First 70 email one by one in that allocated schedule time i.e. 1 hour. After that in next 1 hour it sends the remaining 30 emails.
Note: If you try to send more emails than the limitsgiven by SMTP it leads to stops sending emails after the maximum limit reached. But still it shows Ultimate Newsletter that emails have been successfully sent to your subscriber which will be wrong information. Sometimes the host company will cancel your handshake with them if you exceeds frequency limit set by them. So try to avoid send emails/newsletter more than the frequency limit provided by SMTP.