I have no problem with Gmail since at some point I learned how to keep inbox zero every day.

I pay for fastmail for no Ads and the ability to send mails from my custom domain. DNSimple can only give me a custom email to receive, but not sending.

Use Fastmail tips:

• Find some shortcuts you frequently use

However, I found some things are difficult/awkward to use Fastmail.

• Cannot preview link. I add a link via command+K and forgot to actually add a URL. It still looks like a link but it is somewhat hard to check.
• Cannot linkify text on mobile
• Cannot schedule to send mails