I was looking at the SPF record for my domain and I realise you use v-spf1 mx -all
However as mx requires at least two lookups (one to get the mx hostnames and one to get the ip address), wouldn’t a better record be v-spf1 a -all ? After all that would be one lookup to get the A record (possibly two if there is an IPv6 address (AAAA record) as well,
It’s hypothetical, and to be honest I forgot about dual stack considerations. Certainly in those situations MX is better as it will pick up on both A and AAAA records.