I have sent emails but some have shown up in the "sent" and others went to "outbox"

I went into outbox to send these emails but they have not shown up in sent.

Why is this?

How do I know if emails have been sent and received by the person I'm emailing to.?

Thanks

I have sent emails but some have shown up in the "sent" and others went to "outbox"

I went into outbox to send these emails but they have not shown up in sent.

Why is this?

How do I know if emails have been sent and received by the person I'm emailing to.?

Thanks