As soon as you start a new Campaign, your emails will automatically be scheduled to be sent as quickly as possible. Though, there are multiple considerations that may impact the duration of a Campaign.
The daily limit associated with your Gmail account in Hunter. This value can go from 1 to 400. To limit the risk of being rate-limited by Gmail (in particular if your account has been recently created), we recommend to limit the emails to 100 per day.
Your sending window in Hunter: A narrow window and/or a large delay between emails will increase the duration of your Campaign.
Parallel Campaigns in Hunter: in Hunter, the oldest pending emails are always sent in priority. This means that if you have multiple active campaigns, the new one will have to wait for the oldest ones to be completed before it can actually start being processed.
Emails sent outside of Hunter: we don't have the control on the volume of emails you send outside Hunter (through Gmail, an email client or any third-party). For this reason, we can't be sure we'll be able to reach the daily limit defined in Hunter.
Gmail and GSuite limits: Google limits the number of emails you can send per day (Learn more).
For this reason, when you launch a Campaign, we'll only provide an optimistic duration for it to be completed as there's no certain way to predict the exact delivery date of an email.