Am I writing the SPF record correctly?

Question

SPF

Did I specify the SPF correctly, I would like to know if ip6 will be useful?

"v=spf1 ip4:178.62.246.212 ip6:2a03:b0c0:2:d0::5c7:2001 a mx include:_spf.mail.ru ~all"

Answer 1

Most likely everything is OK, but it depends on how many MX records you have for the domain. SPF is limited to 10 name resolutions (requests to the DNS server). 1 permission is required for "a", another one for "include" but mx requires 1 permission for MX itself + a separate permission is required for each mx entry. If you have more than 7 mx records, which is possible but unlikely, then this spf record will be considered invalid.
ip6 will be useful if in some situations you send emails over IPv6.

Answer 2

v=spf1 include:_spf.google.com ~all
v=spf1 mx ip2a03:b0c0:2:d0::5c7:2001 include:gmail.com ~all

Answer 3

ip addresses can be omitted if they are present in "a" "mx" records
"v=spf1 a mx include:_spf.mail.ru ~all"