Sent emails don't go to the Sent folder until they've actually been sent. Until then they reside in the Outbox; which normally only appears when there is email in the process of being sent. It's easy to forget that the Outbox exists.
I'm not 100% sure of the actual process, but it probably goes something like this; assuming it for a typical IMAP or Exchange email account.
> You send the email.
> The the email server gets told to send the email (email and attachments get copied to server from iPad if not that process is not already complete.)
> Email gets placed in Outbox on server (if it is there long enough, the Outbox will also appear on the iPad)
> Email is transferred and accepted by a receiving server.
> Email is moved to Sent folder on server.
> Email is copied to Sent folder on iPad
As you can see, there are several places where a slow connection or server can cause delays, especially with larger emails and attachments.
I think this is procedure, mostly because it reflects whether an email was actually sent, but is it possible that the iPad considers and email sent as soon as the server has accepted it. In that case there are only two possible delays. The connection and responsiveness of the email server, and the iPad's own processing speed.
Overall, whichever process is used, the most likely cause of of the delay is going to be the same. Your internet connection speed and how fast your email service/server is. That's going to vary a lot. People can expect a lot of variation, not only from person to person, but on particular days.
My email, like Scifan's is usually pretty fast. I have, however, noticed big delays on occasion. Usually when I send large attachments.
