I received an answer through IRC chat:
Either:
- use script at which you can set a max batch size: http://www.limesurvey-templates.com/automatically-send-email-invitations-p-49.html since there is no other in-build feature.
- send all the emails (invitation and reminders) in batches manually
Either:
- use script at which you can set a max batch size: http://www.limesurvey-templates.com/automatically-send-email-invitations-p-49.html since there is no other in-build feature.
- send all the emails (invitation and reminders) in batches manually