I'm sending out a newsletter every now and then. A simple text newsletter that goes out to about 50,000 subscribers. I send it via a PHP script I wrote myself. It can do a/b tests, bounce- and optout-handling. Every time I see commercial offerings like this one, I wonder: Would I gain anything by using them? They seem pretty expensive to me. My selfmade solution also can do HTML mailings, but I never was able to meas…
Deliverability is going to be substantially better. IPs from commercial providers are trusted among ISPs and have a better chance not being flagged as spam.
The unfortunate thing is that every time there's a new trusted mailing service with a good reputation, spammers flock to it.