How to properly configure spf record in DNS for multiple email sending services?

Question

Domain Name System

How much understood SPF for each subdomain are not inherited?
The problem is when I send messages via mailgun/sparkpost and other logs I see the mail is leaving and either 1 out of 10 sent is sent to my mail and then it goes to spam, in general, nothing comes.
Domain on name.com. I use their email forwarding.
I send the message to the mail of the same domain, that is, I expect that mailforwarding name.com will work.
For example, DNS with mailgun settings

# Это то что выставил автоматом name.com видимо для email forwarding
TXT	mydomain.com	v=spf1 a mx ~all
MX	mydomain.com	mx7.name.com	10
MX	mydomain.com	mx3.name.com	20
MX	mydomain.com	mx5.name.com	30
MX	mydomain.com	mx4.name.com	40
MX	mydomain.com	mx8.name.com	50
MX	mydomain.com	mx6.name.com	60

# Достаточный минимум для отправки почты через mailgun
# Поддомен ms.mydomain.com
TXT	ms.mydomain.com	v=spf1 include:mailgun.org ~all
TXT	krs._domainkey.ms.mydomain.com	k=rsa; ...

According to the mailgun logs, the mail is gone

{
...
"event": "accepted",
...
}

The same issue is reproduced with sparkpost as well.
Any ideas

Answer 1

do not forget that in SPF you need to write not the domain itself, but the real mail server.
Since if your mail does not go from the domain, but simply from the IP, then you need to add it to the spf
, and yes, each level 3 domain is a completely different site.
Just open the body of the letter that got into spam and see what is written there, but rather throw it here.
I also recommend reading for
PTR (only with a dedicated IP)
DKIM
DMARC
Also, if you send real spam to clients, then you need to comply with additional requirements, for example, such comrades as mail ru.
THERE are requirements for the letter itself, the ability to unsubscribe, and so on.