Where Are My E-mails Sent From? Should I Create Reverse Ip Lookup

Where am I sending e-mails from with the below settings:

(Is it mail.freesexdoor.com, www.freesexdoor.com, 64.85.161.123 or 64.85.161.124?)

My secondary question is: Is creating own reverse IP lookup to 64.85.161.124 possible and beneficial in my case? If so, what should I replace this SPF line with: freesexdoor.com. TXT "v=spf1 a mx ip4:64.85.161.123 ?all"?

I'm trying to improve freesexdoor.com's e-mail delivery ratio because hotmail and gmail deliver my PHP mailer's sent confirmation e-mails to the junk folder. I've done everything I can to improve the sent headers etc. so there's only one more possible way to improve it: (That I can think of). Freesexdoor.com is hosted on the same server as mitorahgames.com.

DirectAdmin control panel on CentOS 4.4.

My server's primary IP is: 64.85.161.123
My server's hostname is: server.mitorahgames.com

server.mitorahgames.com's Related DNS Settings:
mailA64.85.161.123
server.mitorahgames.com.A64.85.161.123
server.mitorahgames.com.NSns1.mitorahgames.com.
server.mitorahgames.com.NSns2.mitorahgames.com.
mailMX10
123.161.85.64.in-addr.arpaPTRserver.mitorahgames.com.
server.mitorahgames.com.TXT"v=spf1 a mx ip4:64.85.161.123 ?all"

freesexdoor.com's IP is: 64.85.161.124
freesexdoor.com's Related DNS Settings:

freesexdoor.com.A64.85.161.124
mailA64.85.161.124
mailMX10
freesexdoor.com.TXT"v=spf1 a mx ip4:64.85.161.123 ?all"

I'm by the way putting www.freesexdoor.com (PHP reported server name) to the Message ID: field in the e-mail headers. Would putting IP there perhaps work better? If so, which IP?