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This sounds hopelessly naive to me. If the receiver marks it as spam, it's spam. By definition. Work harder to only send emails to people who want them.
but that shouldn't effect the deliverability to everyone else, but thats a reality which has its own problem and has its own countermeasures.
when people asked OP if they had a solution to this, they hand waived it away. all closed sourced mailing list clients have solutions for this.
but anyway since somehow it is 2019 and people want to act like its 2009 on this matter I'll just skip ahead to echo the productive answer someone else left:
this could probably be run through Amazon SES with their DKIM settings
Spam is unsolicited commercial email.
if I sign up on a site, click the 'yes email me' button, and then mark the email as spam when I get it, I am the one acting incorrectly, not the sender who is literally doing what I instructed them to do..
Unsubscribing from email lists can be cumbersome and non-uniform, which is usually why people just hit that spam button instead. It always provides them a uniform interface and largely achieves the same goal from their perspective.
People forget subscribing and hit "Spam", which has an impact on the sender reputation and affects future deliverability for that sender.
One of the factors I didn't mention in previous comment is presence of physical mail address.
Not sure what "unfortunately for me" is in reference to - BigMailer isn't a platform for cold emails (there are plenty others that specialize in cold email campaigns) and Amazon SES doesn't give a free pass on the practice either.
