Huh, I guess I can kind of see that? But at the same time, the shading also really makes it look like an envelope, which is more or less what you'd expect from a mail client. I rather like the bird part of the logo, but the envelope/arrow feels not as prominent or obvious as I'd expect. Still an okay logo, though.
The fact that we're talking about it shows that this is in fact a minor(?) design flaw. Ideally it should be obvious that it is an envelope, not an arrow, so that a user who's never seen the logo before immediately knows what it represents.
Haha yeah, though I could probably also imagine a down arrow logo, for mailbox folders or something. You're right that there's a bit missing for an actually distinctive letter shape, notably the rectangular edges. But those would clash with the circular shape.