On our Premium and Enterprise plans, Yesware's Campaigns feature has a limit of 900 recipients per upload (click here for more info on how to add recipients) and a limit of 5000 recipients per campaign. For Pro plans, it is 20 recipients (the Pro plan will allow 20 recipients/month).
If you are currently on a Yesware trial, there will be a limit of 500 recipients for the duration of the trial.