Help Needed: Running Direct Mail Campaigns for AEs in NYC

Anyone here with experience running direct mail campaigns? I’m planning one targeting AEs in NYC -sending them a small hourglass as a symbol of all the time they’re currently wasting (with a few clever puns thrown in). The concept is solid, but I’ve hit a wall with getting accurate addresses. I reached out to SDRs hoping they’d confirm office details — barely got any responses. I need at least 100 verified addresses from our target accounts. The only backup plan I have right now is calling board lines one by one. What am I missing that should be obvious?