I am using Zimbra 7.1 and postfix with Debian 6.0 and php5. I am using swiftmailer to send my marketing emails out which works great. I have been tweaking my system and since I have added antiflood and usleeps to every email to slow my system down (instead of throttle by swiftmailer).

So I have my anti flood set to 50, which means it sends 50 emails and then waits 15 seconds and opens a new SMTP connection.

After every email it waits 1 second and after every 25 emails it waits 2 seconds.

My question is if I am opening a new SMTP connection every 50 emails, is 2:56:04 enough time to allow to send 9614 emails? Does zimbra limit the SMTP connections?