Open an Outlook .msg e-mail without Outlook

What it shows

• Who and when. From, To, Cc and Bcc with names and addresses, the subject, and the time it was sent. Outlook stores that time in UTC, so it is shown in UTC and in your own time zone, with the delay until it was received.
• The message. The HTML version in a locked-down frame, using the same rules as the .eml viewer: scripts are removed and cannot run, and every image, stylesheet or font that would load from a web address is blocked and counted. Pictures pasted into the message come from the file itself and still show. The plain-text version is one click away.
• Rich-text bodies. A message written in Outlook's rich-text mode may have no text or HTML copy at all, only compressed RTF. It is decompressed here: save it as an .rtf that Word, WordPad, TextEdit or LibreOffice open with the formatting, or read the text preview.
• Attachments with their full file name, type and size, each saved from this tab. An .msg stores attachments as raw bytes, not as base64 text the way an .eml does, so what you save is byte for byte the file the sender attached.
• Attached e-mails. A message forwarded “as attachment” sits inside the .msg as a whole message of its own. It is listed as an attached e-mail, can be saved as its own .msg, and opens right here with the button next to it.
• The Internet headers Outlook kept when the message arrived: every server it passed through with the delay at each hop, and the SPF, DKIM and DMARC results the receiving server recorded.

What it cannot do

• S/MIME-encrypted or signed bodies. An encrypted message can only be opened with the recipient's private key in their own Outlook. The page says the message is encrypted and lists the smime.p7m part, but shows no text. For a signed message the signature is not checked.
• Rights-protected mail. A message sent with “Do Not Forward” or an encrypting sensitivity label arrives as a message.rpmsg attachment encrypted to the recipient's Microsoft account. Only Outlook signed in to that account can read it.
• .pst and .ost mailboxes. These are whole mailboxes in a different file format, often many gigabytes. Only single messages saved as .msg are read.
• Calendar items, contacts and tasks beyond their fields. A meeting request shows its subject, organiser and attendees and, when recorded, its start, end and location, but no calendar view, no recurrence rule and no reply buttons. Contacts and tasks show only what they share with an e-mail.
• Internet headers that were never there. Outlook only keeps headers for mail that arrived from outside. A message sent inside the same Exchange or Microsoft 365 organisation, a sent item and a draft have none.
• Converting. There is no “save as .eml” or PDF: save the attachments, the RTF body, or print the page.

Useful to know about .msg files

What a .msg is

It is what classic Outlook for Windows writes when you drag a message to the desktop or use File › Save As. Inside is a Microsoft compound file, the same container as a Word 97–2003 .doc, holding the message's properties as small streams: __substg1.0_0037001F is the subject, __substg1.0_1000001F the plain-text body. Apple Mail, Gmail, Thunderbird and the mail apps on phones read .eml files and not this format.

Why the file names can look odd

Each attachment carries a long name (Q3 revenue chart.png) and an 8.3 short name (Q3REVE~1.PNG). The long name is used here; the short one only when a very old message has nothing else.

Addresses like /O=EXCHANGELABS/OU=…

A sender inside the same Exchange organisation may be stored with an internal Exchange address instead of an e-mail address. When the .msg also holds the SMTP address, that is shown; when it does not, the internal address is shown and marked as such.

Old .msg files and code pages

Older Outlook versions saved “ANSI” messages, with text in the Windows code page of the sender's PC (1252 for Western Europe, 1251 for Cyrillic, 932 for Japanese). The page reads the code page recorded in the message and decodes the text with it. Messages saved as “Outlook Message Format - Unicode”, the default in current Outlook, need no guessing.

How to get a .msg to open here

From Outlook for Windows, drag the message to the desktop or a folder. From an e-mail you received with a .msg attached, save that attachment first. On an iPhone, save the attachment to Files and choose it from there.