How do I white list Pressero's email server to prevent messages being marked as SPAM?

PRESSERO > *Pressero FAQs
If you need your emails to have a From: address in your own email domain, you may have a problem where such mail is marked as spam after it arrives, or even dropped and not delivered. The cause of this is the common SPF record, described in this article:
Depending on your exact SPF record and mail provider, this can affect you even if you specify your own outgoing mail server in your Subscriber or Site settings! This is because it is the destination mail server that is deciding the mail is unacceptable even after it arrives.
You have two choices to get around this problem. The first choice is to change your SPF record, essentially announcing that Pressero servers are allowed to send mail from your email domain. To do this, you should add:
to your current SPF record.
The second choice is to not use a From: address in your email domain. If you use, then your mail server will not see the mail as spam, because it is not claiming to be from your email domain.