Computer Forensics - Phone Stalking
More commonly known as SPAM, emails that are unwanted are generally deceive where they originate from. Professional Spammers often give false addresses to hide where they come from. There are various ways that Spammers can give false addresses, including by hacking in to other computers, and using their email accounts.
Law Enforcement generally is only able to assist in criminal matters therefore, there is little that they can do in relation to general "spam", such as commercial advertising and campaign mailing, especially if it turns out that it originates from another country. Your internet service provider may be able to provide advice on identifying the origin of e-mail and on selectively blocking messages. If however the spam has offensive material included in it, (e.g. explicit pictures or child pornography), then it is worth contacting your local or national High Tech Crime Unit.
If someone is exploiting personal information about you in order to send you unwanted e-mail they may be breaching data protection laws. In this instance, it is worth contacting you country’s Information Commissioner, or Data Protection Commissioner.
In the UK the authority responsible for overseeing data protection laws is the Information Commissioner. You can find information and advice at the Information Commissioner's website at: http://www.dataprotection.gov.uk . If, however, the emails are coming from abroad, then are likely to be outside the jurisdiction of the Information Commissioner.