SPF DNS Lookup Limit – “Too many DNS lookups” error
Due to the SPF specification limit, the maximum number of DNS lookups allowed is 10. The SPF will fail if your SPF record results in more than 10 DNS lookups. The mechanisms which are counted towards DNS lookups are: ptr, a, mx, redirect, include and exists.
The mechanisms which do not count towards the limit are “ip6″,”ip4”, and “all”.