Some people have already complained about the way GMail IMAP works. With great power comes a great responsibility. Google guys, you have one of the largest email services in the world, so this means that you have to care a lot about users and clients. Dape recently reported and error in how GMail creates the body structure of some particular messages and still got no answer.
Now I found that it does not return the full bodystructure of a multipart/mixed with two refc822 messages in it. If this sounds strange to you, it’s basically how Mozilla Thunderbird creates an email with two other emails as attachments. GMail simply will not tell you about the structure of the two attached emails.
Bodystruct support in Modest is working in most cases although these problems with GMail will most likely mean that it won’t be shipped with the next software update for the N900.