To process in batches, you can configure two variables:
MAILQUEUEBATCHSIZE - the size of a batch
MAILQUEUEBATCHPERIOD - the time to wait until running the next batch (in seconds)
ISPs now have the following option available as well:
They can create a file /etc/phplist.conf that can have the following content:
Maximum size of a batch that can be assigned by any user on the server Any user making a batch larger than this will use this value
Minimum Batch Period that can be assigned by any user on the server Any user making a period less than this will use this value
path to a file that if it exists, blocks sending completely
The last one can be used to disallow sending in certain times of the day.
It only has to exist, no content is read or displayed. I suppose your users
will appreciate if it doesn't exist as certain times as well.