{"id":14,"date":"2026-08-01T03:57:06","date_gmt":"2026-08-01T03:57:06","guid":{"rendered":"https:\/\/easyextract.online\/blog\/eml-vs-msg-file\/"},"modified":"2026-09-21T15:22:04","modified_gmt":"2026-09-21T15:22:04","slug":"eml-vs-msg-file","status":"publish","type":"post","link":"https:\/\/easyextract.online\/blog\/eml-vs-msg-file\/","title":{"rendered":"EML vs MSG File Format: Key Differences &#038; Comparison Guide"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">An <strong>.eml<\/strong> file is one email message stored as plain text, written by almost every mail program \u2014 Apple Mail, Thunderbird, Gmail exports and Windows Mail. A <strong>.msg<\/strong> file is one message stored in Outlook&#8217;s own binary container. They hold the same kind of thing in completely different formats, which is why a .eml opens in any text editor and a .msg looks like gibberish in one.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That single difference \u2014 text versus binary container \u2014 is behind almost every practical question people have about the two formats: which one a program produces, why one won&#8217;t open, and how to read either without the software that made it. Here is what actually distinguishes them, tested against real files.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The short version<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>.eml<\/strong> \u2014 plain <a href=\"https:\/\/datatracker.ietf.org\/doc\/html\/rfc5322\">RFC&nbsp;5322<\/a> text: header lines, a blank line, then the body. Universal. Opens in Notepad, though it looks messy.<\/li>\n<li><strong>.msg<\/strong> \u2014 a Microsoft <a href=\"https:\/\/learn.microsoft.com\/en-us\/openspecs\/windows_protocols\/ms-cfb\/\">Compound File Binary<\/a> container, the same structure a Windows Installer <code>.msi<\/code> uses. Outlook for Windows writes it. Nothing else reads it without a dedicated parser.<\/li>\n<li>Both hold exactly one message. Neither is a mailbox \u2014 that is <code>.pst<\/code>, <code>.ost<\/code> or <code>.mbox<\/code>, which hold thousands.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">What each format actually is<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>.eml<\/strong> is the message exactly as it travelled between mail servers. Open one in a text editor and you can read the <code>From:<\/code>, <code>To:<\/code>, <code>Subject:<\/code> and <code>Date:<\/code> lines directly. The catch is that the parts which contain anything beyond plain ASCII are encoded: a subject with an accent arrives as <code>=?UTF-8?B?\u2026?=<\/code>, and attachments are Base64 \u2014 long blocks of seemingly random letters. It is readable in principle and unreadable in practice, which is the whole reason viewers exist.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>.msg<\/strong> is not text at all. It is a miniature file system inside a single file, with each part of the message \u2014 subject, body, every attachment \u2014 stored as a separate named stream. The names look like <code>__substg1.0_0037001F<\/code>, where the digits are a Microsoft property code. This is why a .msg shows as binary noise in a text editor: there is no plain text to find. It needs software that understands the container.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Which program makes which<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>You got the file from\u2026<\/th><th>It is almost certainly\u2026<\/th><\/tr><\/thead><tbody>\n<tr><td>Dragging a message out of Outlook for Windows<\/td><td>.msg<\/td><\/tr>\n<tr><td>Outlook on Mac, or Outlook on the web<\/td><td>.eml<\/td><\/tr>\n<tr><td>Apple Mail (drag to desktop)<\/td><td>.eml<\/td><\/tr>\n<tr><td>Thunderbird &#8220;Save As&#8221;<\/td><td>.eml<\/td><\/tr>\n<tr><td>A Gmail or Google Workspace export<\/td><td>.eml<\/td><\/tr>\n<tr><td>A system that &#8220;saved the email&#8221; on Windows<\/td><td>usually .msg<\/td><\/tr>\n<\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The rule of thumb: <strong>.msg means Outlook for Windows was involved.<\/strong> Everything else produces .eml, because .eml is the format email itself uses.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How to tell which one you have<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Open the file in a plain text editor \u2014 Notepad on Windows, TextEdit on Mac.<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>If the first lines are readable words like <code>Received:<\/code>, <code>From:<\/code> and <code>Subject:<\/code>, it is a <strong>.eml<\/strong>.<\/li>\n<li>If it opens as a wall of binary characters starting with a few odd symbols, it is a <strong>.msg<\/strong>. (The first eight bytes are always the same signature, <code>D0 CF 11 E0<\/code>, though you will not see that in a text editor.)<\/li>\n<li>If the file is hundreds of megabytes, it is neither \u2014 it is a mailbox (<code>.pst<\/code> or <code>.mbox<\/code>), which holds many messages.<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\">Which should you keep?<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>If you\u2026<\/th><th>Prefer<\/th><\/tr><\/thead><tbody>\n<tr><td>Need the file to open on any computer, now or in ten years<\/td><td>.eml<\/td><\/tr>\n<tr><td>Work entirely inside Outlook for Windows and value exact fidelity<\/td><td>.msg<\/td><\/tr>\n<tr><td>Are archiving for legal or compliance reasons<\/td><td>.eml (open, documented, future-proof)<\/td><\/tr>\n<tr><td>Need to move a message between different mail programs<\/td><td>.eml<\/td><\/tr>\n<\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">For long-term storage, .eml is the safer choice precisely because it is plain text and its format is a published standard. A .msg depends on Microsoft&#8217;s container format and reads best in Outlook \u2014 fine while you are in that world, less so as an archive meant to outlast it.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Common problems, and what causes them<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>&#8220;The .msg file won&#8217;t open on my Mac.&#8221;<\/strong> Expected \u2014 macOS has no built-in support for Outlook&#8217;s container. The message is intact; it just needs a reader that understands the format.<\/li>\n<li><strong>&#8220;The subject is full of <code>=?UTF-8?B?<\/code> gibberish.&#8221;<\/strong> That is a .eml with an encoded-word subject. A proper viewer decodes it back to the real characters; a text editor shows it raw.<\/li>\n<li><strong>&#8220;The attachment saved as a text file full of random letters.&#8221;<\/strong> That is Base64 \u2014 the raw encoding of a .eml attachment. It has to be decoded back to bytes, which a viewer does and a copy-paste does not.<\/li>\n<li><strong>&#8220;The first line of the subject is missing.&#8221;<\/strong> Usually a byte-order mark or a folded header that a naive parser mishandled. Reader software that expects these keeps the whole subject.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Reading either one without the mail client<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">You do not need Outlook, or any account, to read either format. EasyExtract has a viewer for each, and both run entirely in your browser \u2014 the message is opened on your own device and never uploaded, which matters because a saved email is real correspondence.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong><a href=\"https:\/\/easyextract.online\/msg-viewer\/\">Outlook MSG viewer<\/a><\/strong> \u2014 opens a .msg, shows the sender, recipients, date and body, and saves every attachment at full size.<\/li>\n<li><strong><a href=\"https:\/\/easyextract.online\/eml-viewer\/\">EML viewer<\/a><\/strong> \u2014 opens a .eml, decodes the headers and Base64 attachments, and shows the body as text.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Both show the message body as text rather than rendering its HTML, so tracking pixels never load and links are never live \u2014 the safe way to read a message you are not sure about.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Frequently asked questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Can I convert a .msg to a .eml?<\/h3>\n\n\n<p class=\"wp-block-paragraph\">Yes, but it is a genuine conversion between two different containers, not a rename. Outlook for Windows can save a message as .eml directly; on other systems, a viewer that reads the .msg and re-exports the message is the practical route. Simply changing the file extension does not work \u2014 the bytes inside are still Outlook&#8217;s binary format.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Is one format more secure than the other?<\/h3>\n\n\n<p class=\"wp-block-paragraph\">No. Both are just containers for the same message, and neither encrypts anything by itself. What matters for safety is how you open the file: a viewer that shows the body as text rather than rendering its HTML will not load tracking pixels or activate links, regardless of whether the source was .eml or .msg.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Why does Outlook use .msg instead of the standard .eml?<\/h3>\n\n\n<p class=\"wp-block-paragraph\">The .msg format predates the web-era standardisation of email files and stores Outlook-specific properties \u2014 categories, flags, internal fields \u2014 that plain RFC&nbsp;5322 has no place for. It is higher fidelity inside Outlook, at the cost of portability everywhere else.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Which opens on the most devices?<\/h3>\n\n\n<p class=\"wp-block-paragraph\">.eml, by a wide margin. Because it is plain text following a public standard, essentially every mail program on every operating system can read it. A .msg reliably opens only in Outlook for Windows, or in software written specifically to parse its container.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Sources<\/h2>\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/datatracker.ietf.org\/doc\/html\/rfc5322\">RFC 5322: Internet Message Format<\/a> \u2014 the standard a .eml file follows.<\/li>\n<li><a href=\"https:\/\/learn.microsoft.com\/en-us\/openspecs\/windows_protocols\/ms-cfb\/53989ce4-7b05-4f8d-829b-d08d6148375b\">[MS-CFB]: Compound File Binary File Format<\/a> \u2014 the container a .msg file uses.<\/li>\n<li><a href=\"https:\/\/learn.microsoft.com\/en-us\/openspecs\/exchange_server_protocols\/ms-oxmsg\/\">[MS-OXMSG]: Outlook Item (.msg) File Format<\/a> \u2014 how a message is laid out inside that container.<\/li>\n<\/ul>\n\n","protected":false},"excerpt":{"rendered":"<p>An .eml file is one email message stored as plain text, written by almost every mail program \u2014 Apple Mail, Thunderbird, Gmail exports and Windows Mail. A .msg file is one message stored in\u2026<\/p>\n","protected":false},"author":2,"featured_media":33,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"slim_seo":[],"footnotes":""},"categories":[3],"tags":[],"class_list":["post-14","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-guides"],"_links":{"self":[{"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/posts\/14","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/comments?post=14"}],"version-history":[{"count":3,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/posts\/14\/revisions"}],"predecessor-version":[{"id":130,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/posts\/14\/revisions\/130"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/media\/33"}],"wp:attachment":[{"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/media?parent=14"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/categories?post=14"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/easyextract.online\/blog\/wp-json\/wp\/v2\/tags?post=14"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}