does anyone have experience using haraka vs a service like sendgrid? I'm curious if there are any challenges with mail deliverability such as the haraka instance being flagged for spam.
There's definitely more work required to set up, warm up and to deal with blocklists when self-hosting. Basic stuff like DKIM/SPF/DMARC is a must in both cases.
As a Postmark customer, I strongly recommend switching to their service if you want better deliverability than Sendgrid, for example. However, if you have a poorly sanitized email audience, you'll suffer a lot of pain initially to reduce the bounce ratio.
It's like switching from a gym where you're on your own and no one cares to one where you're yelled at if you miss your training. Naturally, the former delivers much better results, but there is an adaptation period which makes a lot of people give up.