Spent the last month setting up around six thousand Azure mailboxes for a client. SPF, DKIM, DMARC all locked in, warmup running like clockwork. first week open rates looked promising, then they just fell off a cliff.
took me longer than I'd like to admit to pinpoint the issue. by default, Azure assigns shared IP pools for outbound SMTP - and those pools are essentially pre-burned. It's like moving into a flat where the previous tenants ran a spam operation, your reputation is shot before you've typed a single subject line.
i run the same campaign out of Google Workspace boxes and they're still hitting opens around 40-45%. Meanwhile Azure crawled to about 10%. The culprit is that shared pool.
if you're on Azure and your deliverability feels broken, check which IP pool you're actually sending from. the out-of-the-box config just isn't built for cold email - it's a lesson I won't forget.
