Yes, they can monitor almost anything related to your email by obtaining information from your internet service provider. However, keep in mind that the police must truly want you in order to search down deleted emails or other material. They cannot simply go ahead and do so without a court order.
The best way to protect yourself against warrantless searches is not to send any sensitive information through email. Instead, use a phone call, a written note, or meet in person before sharing such information. This will help ensure that you aren't revealing anything incriminating during these exchanges.
In addition, be sure to delete messages in appropriate periods. If you are using Gmail, for example, you can set up automatic deletion if you don't open an account's inbox within a certain time frame. This will help prevent old emails from being displayed when users conduct Google searches for their names.
Finally, only communicate via secure channels where you can feel confident that your conversation isn't being monitored. HTTPS connections display a lock icon in the address bar of your browser to indicate that you are communicating with a secure website.
Since law enforcement agencies can access your email regardless of whether it has been deleted, be sure to delete important messages promptly. This will help prevent your email account from being used as a tool for committing crimes.
Yes, but only if the email account is not completely destroyed. The cops can trace the email account throughout that particular period. And the police have no recourse if the email account is totally wiped, i.e. after the time period has expired.
So, certainly, the cops may look through your email if necessary, and your ISP will gladly "report you out." If police feel your email includes evidence, they will normally get a warrant.
However, most people use their email account for personal matters. So unless the police have any other reason to suspect you, they probably won't search your email account when doing their job.
Also, it's important to remember that just because you send an email from an address, doesn't mean anyone else does too. Some people use free web-based email services such as Gmail or Yahoo! Mail, which can't be traced back to an individual user.
Finally, make sure you delete all messages in your inbox at least once per month. This goes for all your emails, not just those sent from your phone. Failure to do so could result in legal issues for you down the road.
Everything that has ever been sent through your computer is always there. If you remove it, you can still restore it at a later time.
The way the question is asked lends itself to this answer: the police can identify where the email was sent from. They would have to investigate further (including talking with the owner of the email account and examining his/her computer, etc.) to determine who was the sender. However, there are many ways to send an email that the police could not trace back to a particular person.
Here are some examples of how emails can be sent anonymously:
Bounce messages - When you try to send an email to one address but it gets sent to another instead, that other address is called a bounce point. The original addresser will know that someone else received their message, but they won't know who. Bounce messages are common when sending mail through free web-based services like Gmail or Yahoo! Mail because they don't keep track of which addresses sent messages previously.
Cut-and-paste jobs - This method involves copying and pasting text into an email and clicking the "Send" button. The person reading your email would see everything exactly as you did, including any obvious errors. However, someone who has never seen these copies and pastes would have no idea that they were not originals.