SpamAssassin test says "SPF:HELO does not match SPF record"

I've got a single server with a single IP and I'm setting up a single domain at this time. I'll be adding a few more later on and want to send from them, but at the moment, I'm trying to properly configure SPF. It seems to be properly configured according to test via google, but testing via mail-tester.com says "SPF: HELO does not match SPF record (fail)" and points me to the page on the SPF site which says the following:

"mail-tester.com rejected a message from a mail server claiming to be mars.domain.com.

mail-tester.com received a message from mars.domain.com (xxx.xxx.xxx.xxx) from a mail server claiming to be mars.domain.com.

However, the domain mars.domain.com has declared using SPF that it does not send mail through mars.domains.com (xxx.xxx.xxx.xxx). That is why the message was rejected."

I've been reading the SPF documentation repeatedly and still can not exactly comprehend what is the correct syntax to use. Here is my current DNS.

MX

mars.domain.com 10

A

xxx.xxx.xxx.xxx

• xxx.xxx.xxx.xxx

www xxx.xxx.xxx.xxx

mars xxx.xxx.xxx.xxx

TXT

v=spf1 mx -all

• v=spf1 -all

www v=spf1 -all

mars v=spf1 mx -all

As far as I understand, I have told it "hostnames that appear in mx records and have a matching A record are allowed to send". Which, in this case, you can see it is…

So exactly what is missing, here?!

openspf's page is suggesting I change it to "v=spf1 mx a:mars.domain.com -all" which seems unnecessary. I already have mars.domain.com with an SPF record and an A record, which should match the "mx" part of the spf1 definition, right?