If you want to compete with the big players, you have to solve the most important pain point and work upward from that small use base.
My case: I work on https://hanami.run (will soon move to https://mailwip.com due to hanamirb.org conflict) and email forwarding is very competitive. Big and old players are all over the place because at the end of day, setting up email forwarding isn't hard and many open source project did it, heck you can spin up AWS lambda for incoming email in no time.
The pain point is: email will drop sometime, time to time no matter how good an email forwarding service is because they have to scan spam, have false positive, or because of strict DMARC/SPF rule. And I have no tools available to help me out there. So I focus strongly on my maillog features with many level of privacy:
- no log at all: defaut
- only log spam email: give you another chance to read email on our UI
- log meta data
- log meta data + subject
- log whole email
Then, next steps is regex forwarding.
Again, I learned this from reddit, forum search of those use base.
Basically I focus on those small features that big player doesn't have.
Then I was able to obtain a very small user base who has issues with big providers. Then I work upward from there to spin out given now that I had a working and good product that people are willing to pay for.
The rest is just iteration.