What is the way out if DKIM is not supported by the host?

Question

SPF

Good afternoon! I use software for organizing mailing lists and faced with the fact that a lot of emails end up in SPAM. I found a solution on the Internet that says that you need to configure DKIM and SPF.
No problem with SPF. But the DKIM hoster said that it does not support it.
I would like to understand what are the ways to reduce the hit of letters in SPAM? Is an SPF record sufficient, or is DKIM mandatory?
In one of the topics I saw that they sent out 30,000 letters using only SPF and TPR records. Is it really enough?

Answer 1

My clients spit 15k emails once a week on SPF+PTR and correct hostname/A - everything is ok. In Google and Yandex not in spam.
You can use an external service to send signed emails.

Answer 2

SPF and PTR are enough.
The only thing is if you have several IPs, then you need to forcibly limit the sending of messages from the same IP that the domain has, otherwise the PTR will not be equal and a message will come from mail ru that servers with dynamic addresses are ignored.
Also, if you have delegated mail to other services, do not forget that mail de facto leaves not only from there, but also from the local machine, and therefore all IPs must be taken into account.