Every so often (seems to be roughly 1% of the time) DavMail will serve me a blank email. If I try to rerequest the same email a little while later it works fine. I've attached a portion of my log file which relates to this happening.
The relevant line seems to be:
2014-06-25 22:53:46,404 DEBUG [ImapConnection-53490] httpclient.wire.content - << "The custom error module does not recognize this error."
Searching around this seems to be a fairly common issue with OWA2010 and also a transient one (which would explain why I'm later able to request the email successfully):
I realise that this is an issue with my company's mail server but it also seems to be something that DavMail should recognise and react to also (rather than just returning a blank email).
On a hunch I've switched from using Dav to EWS as the protocol and have not yet been able to recreate this issue.