An MSG file is an Outlook item, such as an email with its attachments, saved on disk. Microsoft defines it in MS-OXMSG: a binary compound file with storages and streams, like folders and files inside one file. Properties sit in a property stream, and each recipient and each attachment has its own storage. The e-invoice is the attachment, not the message. Klarbon support is planned, not available yet.
What is in an MSG file?
| Part | Holds |
|---|---|
__properties_version1.0 |
the property stream of the message, such as subject and dates |
__recip_version1.0_#00000000 and following |
one storage per recipient |
__attach_version1.0_#00000000 and following |
one storage per attachment, with its data and file name |
__nameid_version1.0 |
the mapping of named properties |
| Property | Value |
|---|---|
| Container | Compound File Binary format |
| Specification | Microsoft MS-OXMSG |
| Items | email, appointment, contact, task and others |
| Sender details | not proof of who sent the message |
Microsoft publishes the format and shows how a message with recipients and attachments maps to storages and streams (MS-OXMSG, structure).
MSG or EML?
| MSG | EML | |
|---|---|---|
| Standard | Microsoft MS-OXMSG | IETF RFC 5322 and MIME |
| File | binary compound file | text |
| Opening requirements | software with MSG support | mail software with EML support |
What does Klarbon do with MSG files?
Klarbon does not open MSG files today; taking the e-invoice attachments out of an MSG file is planned, not available yet. Klarbon does not run anything embedded in a message. You can forward the email itself to your Klarbon email-in address; see read e-invoices by email.
Related
Frequently asked questions
What is an MSG file?
An Outlook item saved as a file, such as an email, appointment, contact or task. Microsoft defines it in MS-OXMSG. It is a binary compound file, with storages and streams like folders and files inside one file.
How are attachments stored in an MSG file?
Each attachment has its own storage inside the file, holding the attachment's properties and data. An attached email can itself be a message inside that storage.
How is MSG different from EML?
EML stores an email in the open, text-based Internet Message Format of RFC 5322. MSG is Microsoft's binary format for Outlook items. Both can hold the same email and attachments.
Is an MSG file safe to open?
It is as safe as the email inside it. Attachments can be harmful, and the sender shown can be forged, so treat an MSG from an unknown source like any unexpected email.
Sources
- Microsoft, [MS-OXMSG] Outlook Item (.msg) File Format learn.microsoft.com
- Microsoft, [MS-OXMSG] from Message object to .msg file learn.microsoft.com