Conversely, if you aren't sending spam, you talk to the Receiver and have
them talk to their email administrator, manufacturer of their mail software
or their ISP to figure out why your messages are ending up in their Junk
Mail.
You don't get a choice.
You don't get to define the recipient's rules.
You don't get to modify the recipient's spam filters.
You aren't in control of delivery of your e-mails.
You could ask the recipient to add you to their whitelist.
You could check your e-mails that they don't qualify as spam.
You could ensure that you aren't on any public DNS blacklists.