Each of your email domains should have a valid SPF record.

The most important thing about setting up SPF is to get it right. If the record is incorrect, there may be issues with deliverability.

When you create your SPF be sure to include all IPs, hostnames, domains, etc... that are allowed to send as the domain you are setting the SPF up for.

Here is a website that we like to use to create SPF records… https://www.spf-record.com/generator

Example…

Let’s say that domain mailsbestfriend.com needs an SPF record. Let’s say they also use a bulk mailer service such as MailChimp for their outbound email blasts. Here is what the SPF would need look like…

v=spf1 a mx include:servers.mcsv.net –all

What this means…

“a” means the mail server is allowed to send e-mails via the IPv4 and IPv6 addresses of the domain.
“mx” means that the mail server is allowed to send from the registered MX servers.

At the very least, an SPF should have “a” and “mx”

“include:servers.mcsv.net”

The above is the entry that allowed MailChimp to send as the domain.

The “all” switch can be used in 4 ways…

-all – Fail. Non-compliant emails are rejected
~all – SoftFail. Non-compliant emails are accepted, but marked
?all – Neutral. Emails are expected to be accepted
+all – No emails are rejected for SPF failure

If you are 100% positive that your SPF record includes everything that it needs to be correct, you should use the –all

If you are not 100% sure, the ~all would be best.