As well explainedhere: http://docs.phplist.com/PhpListConfigSendRate I consider a super useful tip to add distance between an email and another:
# to avoid overloading the server that sends your email, you can add a little delay
# between messages that will spread the load of sending
# you will need to find a good value for your own server
# value is in seconds (or you can play with the autothrottle below)

Comments

jose reyero’s picture

jose reyero commented
Status: Active » Closed (works as designed)

Both, messaging and notifications modules have 'Limits for queue processing' settings which is actually the same.