Email messages are often sent directly between email accounts and read over webmail services, mobile devices or through email client software. You can, however, also save an email message directly as a file and transfer it through other means, such as via instant messaging or on removable media. Opening these files typically requires a desktop email client or other compatible program.
Email messages saved as files use the file extension EML. These files contain all the same information as a regular email file, including hyperlinks and file attachments. If you open it in a text editor such as Notepad, the message itself is displayed as plain text, without any formatting like font types, bold or italics or colored text.
A wide range of programs can open EML files, mostly desktop email clients. These include Microsoft's Outlook, Mozilla's Thunderbird, Windows Mail, Eudora 7, Entourage, Mac Mail and many others. Interestingly, these files can also be opened in Internet Explorer, provided you change the file extension from ".eml" to ".mht." MHT files are Web page archive files saved using Internet Explorer, but the formatting is nearly identical to EML files.
Issues with Using EML Files
EML files have some restrictions that can limit their usefulness. Their plain text display means that any text formatting is lost, which can diminish the impact or intent of the message. When opened outside of an email client, attached files can't be accessed.
Solutions to EML Issues
Invariably the solution to all issues presented by opening EML files is to just use a desktop email client. This displays all the information as it was intended, restoring the file and all of its formatting and attachments, even if you have previously opened it in a program in which these items were not accessible or visible.