[mlmmj] Problems with spam filters

Despite it being neat software, I'm finding it near impossible to run 
mlmmj mailing lists because mail is being treated as junk by big mail 
outfits such as hotmail and btinternet.

My own mail server (which includes rspamd) accepts mlmmj mailing list 
mail without a problem. And I can observe that my mail, as received, is 
checked to be valid for DKIM, SPF and DMARC. I've also checked some mail 
against e.g. mail-tester.com and not found any problems.

My mail server is not blacklisted anywhere.

Despite this, a number of recipients seem to have messages routinely put 
in junk, and they don't all monitor junk. This creates a big problem, 
and makes a mailing list unusable.

Obviously, I have no influence with hotmail, btinternet, etc who 
probably wouldn't even reply to me.

It seems that big commercial outfits want to force people into paid 
services and to prevent them using simple but valuable mechanisms such 
as an ordinary mailing list.

Is there anything I can do to deal with this problem?