Broken attachments in Apple Mail

Once in a while I seem to have broken attachments in my e-mails in Mail.app.
But when I check those e-mails with another client or webmail everything is all right.

I found out, that one can work around this issue by rebuilding the Mailbox’s Index:

Mailbox-Menu -> Rebuild (last entry)

After a couple of minutes (depending on the size of the corresponding mailbox) my attachments look alright again.