I have a close friend who I won't name. He has a note on his LinkedIn that says "I will never buy anything from you if you call me or email me without you asking" with a list showing the people and companies that have screwed up.

I have literally seen him talk to someone and be like "hey, check my linked in again" just to have them react to their name and company being on the list. You don't need to market to developers, a good product only needs three things: what it costs, documentation that is usable and code snippets I can run my preferred language.

Your email campaign is rarely ever going to help me unless the email specifically tells me what you're product does for me and doesn't include any bullshit marketing or other whitepaper crap.