I was a little skeptical of Microsoft based email deliverability via sparkpost, even with the dedicated IP because the cost was so low ($20/m).
But since my last post, emails to aol and Microsoft recipients started landing in the inbox.
I had a pretty small scale, natural warm up period going on for 7 days with sparkpost and a dedicated ip.
Email settings on this site are set to daily digest, alert even if active and everything else is on the default setting. User growth is small and looks like the attached screenshot if anyone is interested.
I’ll be staying with sparkpost, good so far and very cost effective.
PS - Not sure if this matters for anyone but Ive found both sendgrid and sparkpost accounts without dedicated IPs to always be on one blacklist or another. It used to be better so this is kind of a bummer. Time to spend a little for email.