Please advice how is possible to set up delay between messages? Sometimes GSM operator require SMS to be sent not faster then 1 message each XX seconds.
I don’t think this kind feature available it depends on what Bulk SMS API you have integrated. It would be interesting to know if this feature available.
smstools doesn’t support a throttling itself. would be necessary to throttle via playsms. but that is currently not possible as far as i know.