My host has an hourly sending limitation
Upgrade to a dedicated server
Use an external delivery service
Each message takes 5 seconds to be sent
Do you have a big file attached to your Newsletter?
Do you have the option "embed pictures" enabled on the AcyMailing configuration page?
You're using an SMTP server?
You have an old version of AcyMailing 5
Each message takes 1 second to be sent... but it's still too slow for me!