Which Software/App/SaaS you must use because there is no better alternative?

Wow, what a smart way to find problems!

For me, it would be Postmark. It's more expensive, but I know for sure that my transactional emails will be delivered.

It's crazy, because I started with Sendgrid (I even took a paid plan) with which I had some experience. But at some point I realised that my outlook and hotmail customers were not receiving transactional email. For a company like ours, this is really bad! I have paying customers, I'm paying for a mailing service, yet my mails are not being delivered! (And that's with an opening rate of around 70%, without a single spam complaint)

I did look elsewhere, but it seemed like the other providers were more suited for marketing, or they didn't really have transparent pricing.

For me, its hubspot. I haven't found a better crm, marketing automation and sales automation suite for a better price. I was looking for a replacement for couple of years now.