EML vs MSG
Two ways to save one email. One is a standard, the other belongs to Outlook.
Not sure which one you have?
Drop the file in. The format is detected from its contents, not its name, and either one is read.
Open the viewerOr read the comparison below.
The difference in one table
- Format — EML is plain text (RFC 5322); MSG is a binary OLE2 container.
- Owner — EML is an open internet standard; MSG is Microsoft's.
- Who writes it — EML: Thunderbird, Apple Mail, most webmail exports. MSG: Outlook.
- Who reads it — EML: almost anything. MSG: Outlook, and tools that implement the format.
- Headers — EML keeps the original internet headers. MSG keeps MAPI properties, and the original headers only sometimes.
That last point matters more than it sounds: the original headers are what let you check where a message really came from. An MSG file does not always carry them.
Telling which one you have
The extension is the obvious clue and the least reliable one, because files get renamed.
A better test: open it in a text editor. If the first lines read like
Received:, From:, Subject:, it is an EML. If you
see a run of binary characters, it is an MSG.
Which to keep
If you are archiving messages that may need to be read years from now, or by someone else, keep EML: it is a published standard, it is text, and it will still be readable when today's software is gone. Keep MSG only when you need something Outlook-specific, such as calendar or task properties.
For anything that has to be filed, read by a third party or produced as evidence, exporting to PDF beats both.