v=spf1

This defines the version of SPF being used. v=spf1 is the only valid version currently in use for SPF records.

include:<domain>

This tag includes the SPF record of another domain. It is often used to authorize third-party email providers to send emails on behalf of your domain.

ip4:<address>

This specifies an IPv4 address or range that is authorized to send emails for your domain.

ip6:<address>

This specifies an IPv6 address or range that is authorized to send emails for your domain.

mx

This tag authorizes all mail servers listed in your domain's MX records to send emails.

a

This authorizes the IP address of the domain's A record to send emails.

-all

This defines a strict policy, meaning emails from unauthorized sources will be denied and rejected.

~all

This defines a soft fail policy, meaning emails from unauthorized sources will be marked as suspicious but still accepted.

?all

This sets a neutral policy, meaning emails from unauthorized sources will neither be allowed nor denied explicitly.

redirect=<domain>

This tag redirects to another domain's SPF record for evaluation. It is used for centralized management.

exp=<domain>

This specifies a domain that provides a detailed explanation for SPF failures.