We impose no sending limits, you should tune your campaign to suit your VPS resources and your recipients mail servers limits.
The processing speed depends on your VPS resources , email message size, internet connection and the number of threads you have defined in software options.
Customers can send UNLIMITED number of emails per month, normal speed of VPS [SMTP-1 for ex.] is about 800-1,000 emails/hour. But we recommend sending not more than 10,000 -15000 emails per day from any VPS in order to keep it in the safe zone without spam complaints, taking in consideration that a message body not exceeding 10KB and recipient list segmented into 25 recipient in BCC for each email.
If you want to send in more emails per day and your list isn't very pure opt-in's, you should get more VPS's and load balance your campaign.