Hi,
Regarding your inquiry about the optimal batch size for sending emails, there are several factors to consider. These include the speed of your server, the size of the emails, the maximum runtime of the script, the daily email volume, and the limitations imposed by your Acymailing plan.
Given these variables, it is difficult to provide a definitive answer. However, I encourage you to calculate the batch size that best suits your specific needs. If you require further assistance, please provide us with more detailed information, and we will be glad to assist you.