If they allege a "technical issue", including spam filtering, then they can access, read, preserve, and disclose anything in your mailbox. Since they probably do spam filtering for everybody (both for incoming and outgoing mail), then they have the right to read and disclose the contents of your email at any time.Link (Thanks, John!)
Many spam-filtering services send copies of alleged spams to some central location. If they get N copies of similar messages, they declare it spam and publish the offending messages on the web. Google's right to send your spam to such services gives them the right to send ANY of your email to ANYONE -- for publication.