The reason for the failure is:
Authentication-Results: hotmail.com; spf=softfail (sender IP is 18.104.22.168) email@example.com; dkim=none header.d=example.com; x-hmca=fail firstname.lastname@example.org
The IP address 22.214.171.124 does not appear in your SPF record as either
mx(mail.example.com which resolves to 126.96.36.199),
ptr (p-23-229-191-2.ip.secureserver.net), or the stated domain of secureserver.net.
There may be other solutions, but one simple one is to add the IP address 188.8.131.52 to your SPF record.
v=spf1 a mx ptr IP4:184.108.40.206 ptr:secureserver.net ~all
You can test SPF records at http://www.kitterman.com/spf/validate.html. My previous edit of using the
include mechanism is not correct because secureserver.net does not have a valid SPF record. Apparently the record for example.com has already been changed to something similar to the above recommendation using the
No DKIM header is present. You can test your DKIM configuration at http://dkimcore.org/tools/ among other places, but the problem of the header not being present is a server configuration issue that is probably resolved by referring to the documentation for the various tools you are using.
It is also important to note that there is no guaranteed way to not arrive in spam folders other than to develop a good reputation and gain the trust of the various email providers. SPF and DKIM help primarily because they offer some protection against spammers that may try and use your domain in their spamming efforts.