[alphabettsy]

Spark stores your email credentials and some of your mail on their servers. No-go for me.

[growtofill]

Fastmail’s per-app password is a feature to handle this.

[alphabettsy]

And Gmail uses OAuth. How does that change that fact you are giving some 3rd party access to your email?

My main concers are why they would provide a free service and what security they have in place.