It is because all the others provide some way to send an E2EE email. The issue with Skiff is that it is difficult to make that initial share without using some other product first.
Sharing a document on a collaboration suite, isn’t the same as an immutable copy with a date on it at a particular point in time.
The email header functionality is crucial for determining whether someone is the target of spearfishing. Some scammers will go to some effort to find out a lot about a victim, their org and then try to pretend to be someone within that org. All our current recommendations allow for this.
That was not part of the evaluation, but something I noticed along the way. It was worth mentioning because it is a feature that users may have had with other providers that they will lose when importing their mail into Skiff.
The last client I migrated had over a thousand directories. They had been using email for 20 years and had about 40k emails. They did not want to lose that structure, and it was necessary that the product I selected for them supported that feature.
The first tier of paid usage on Skiff is quite a bit more than it’s competitors. Sure, you do get more storage, but quite often a user won’t have 100GB of email or files to store. This impacts your product, because it means that a lot of people will stay on the free tier, which doesn’t make you any money. Money is needed for viability, and its important that the company remains healthy.