Who owns the "content"
Looking at Google's terms of service, I'm not surprised. It seems that you give away your rights for all content you put in (e.g. emails you write and send) but Google' recognise they have no rights over stuff inbound to you.
Can't use inbound (but if they do it's your problem to notice and act accordingly):
9.4 Other than the limited license set forth in Section 11, Google acknowledges and agrees that it obtains no right, title or interest from you (or your licensors) under these Terms in or to any Content that you submit, post, transmit or display on, or through, the Services, including any intellectual property rights which subsist in that Content (whether those rights happen to be registered or not, and wherever in the world those rights may exist). Unless you have agreed otherwise in writing with Google, you agree that you are responsible for protecting and enforcing those rights and that Google has no obligation to do so on your behalf.
But you give away outbound:
11.1 You retain copyright and any other rights you already hold in Content which you submit, post or display on or through, the Services. By submitting, posting or displaying the content you give Google a perpetual, irrevocable, worldwide, royalty-free, and non-exclusive license to reproduce, adapt, modify, translate, publish, publicly perform, publicly display and distribute any Content which you submit, post or display on or through, the Services. This license is for the sole purpose of enabling Google to display, distribute and promote the Services and may be revoked for certain Services as defined in the Additional Terms of those Services.
So that's why I don't use it!