Typically, the best source of email evidence is the email server. While emails may be found in multiple locations such as on a phone, tablet, or computer, those locations tend to hold fewer emails than the server. For example, many phone users have their emails synced for only 30 days, and maybe only six months on their computer. Whereas the email server may have three years or more worth of email. Therefore, frequently the email server is the preferred source of evidence.