How Do I Increase The Speed Of Sending Emails Using The Mail Service on my Mac Mini Server?

Note: This is the first time I have set up a mail server.
I have a Ruby on Rails application where I am currently sending approx. 240 individual emails with the potential of more being sent each week as more people add themselves to our mailing list. I am sending them invidually in order to personalize the emails and to hopefully prevent my emails being falsely identified as spam.
The GoDaddy email address I was using in my Rails application has a daily limit of sending 250 emails each day. With our mailing list fastly approaching 250 I decided to set up an email address on my Mac Mini Server using Mountain Lion (OS X Server). The email address was set up to be stored locally at the advice of Apple Enterprise Support. This email address will not be used in an email program. It will only be used in all my Rails applications.

My emails send properly but take almost 10 seconds an email. When I use the same software with GoDaddy's email address the emails take about eight minutes to send. With the email address I created it takes about 41 minutes. The difference seems to have to do with the sacl_check being done. Here is an example of what I see for each email in mail.log.

Mar 14 11:06:50 hostname.domain1.com postfix/qmgr[45322]: 4B2C5603D25: removed
Mar 14 11:06:59 hostname.domain1.com postfix/smtpd[99464]: sacl_check: mbr_user_name_to_uuid(emailuser@emaildomain.com) failed: No such file or directory

There is 9-10 seconds that elapses when the sacl_check. If I subtract this difference the remaining time is almost the time that the GoDaddy email takes to send the same number of emails.

The link below is a post about the sacl_check. I was looking at the comments by powercore from Germany at the comments where settings in /etc/postfix/main.cf are discussed.

https://discussions.apple.com/thread/3241121?start=0&tstart=0

Will making these setting changes speed up the sending of the emails from my Mail Server or is there something else I can check?