Yes, you are correct. It does happen even if you are not downloading the email to a computer. The problem appears to happen most frequently with large attachments, but sometimes it happens with emails without attachments. The interesting thing about it is that if you the read the iphone manual, the mail program is not supposed to download attachments to emails immediately. It is supposed to download all emails and then when you click on an email you can select the attachment at the bottom and only then will it dowload the file. If it really did work that way it would make mail much more effective and efficient. It is definately an annoying bug. Make sure to report this bug to Apple, the more people that report it, the more likely they are to fix it.