Open an OLM file — without Outlook for Mac
Drop an Outlook for Mac .olm archive and browse, read, and search it right here — on any OS, with nothing installed. The file is parsed on your own machine and never leaves your device.
How do I open an OLM file without Outlook for Mac?
An OLM is less exotic than it looks: it is a ZIP container holding one XML document per message, using OPF-prefixed elements such as OPFMessageCopySubject and OPFMessageCopyHTMLBody, with attachments stored in the same ZIP and referenced by OPFAttachmentURL. Any tool that can unzip and parse XML can read one — Windows Outlook, Apple Mail, and Thunderbird simply never implemented it. Mailward does exactly that in your browser: the archive is unpacked and parsed locally, nothing is uploaded, and browsing, reading, and full-text search are free on any OS. One trap for anyone handling OLM data: Outlook for Mac writes every timestamp as UTC with no zone suffix (2022-05-26T17:55:40, no Z), so software that parses those as local time silently shifts every date in the archive — Mailward treats them as UTC.
Drop the .olm file — it is read locally, nothing is uploaded.
Browse the folder tree and open any message with its attachments.
Search across every folder by subject, sender, or body text.
Export one message free, or batch-export with the one-time license.
Open an OLM file — without Outlook for Mac
An OLM is the archive Outlook for Mac exports — and almost nothing else on earth opens one. Windows Outlook cannot read it, Apple Mail cannot import it, and the usual advice is to buy a $40-plus converter or upload your whole mailbox to a stranger's server.
Mailward reads the OLM directly in your browser: folder structure, messages, and attachments, parsed locally in a Web Worker with nothing uploaded. Reading, browsing, and search are free; batch export of folders or search results to open formats is the one-time paid step.
Bring an archive from an old Mac and read it on whatever machine you have today.
Inside an OLM file
OLM is barely documented anywhere, so here is what it actually is, from having written a parser for it. An .olm file is a ZIP container. Inside, each message is its own small XML document named message_00001.xml, message_00002.xml and so on, with elements named by an OPF prefix — OPFMessageCopySubject, OPFMessageCopyFromAddresses, OPFMessageCopyHTMLBody — and the folder tree is simply the directory layout: a message stored at Local/Inbox/message_00001.xml belongs to Inbox. Attachments are not embedded in the XML; each one is its own file elsewhere in the same ZIP, referenced by an OPFAttachmentURL attribute alongside its display name (OPFAttachmentName), MIME type (OPFAttachmentContentType), and Content-ID (OPFAttachmentContentID).
Senders and recipients are structured data, not header text. Each address is an emailAddress element carrying two attributes — OPFContactEmailAddressName and OPFContactEmailAddressAddress — grouped under OPFMessageCopyFromAddresses, ToAddresses, and CCAddresses. The display name and SMTP address arrive pre-split, which is convenient to read but means any tool exporting to .eml has to compose RFC 5322 headers itself, including quoting display names that contain commas. Bodies come in pairs too: OPFMessageCopyBody holds plain text and OPFMessageCopyHTMLBody the HTML — in our cross-validation against an independent implementation, every message carried an HTML body.
What the XML does not contain is a transport header block. There is no Received chain anywhere in an OLM — thread metadata survives (OPFMessageCopyThreadTopic, OPFMessageCopyThreadIndex), but the routing history is discarded the moment Outlook for Mac exports. Two field lessons from real archives: some OLMs skip the usual emails/email wrapper and put OPFMessage* elements directly under the XML root, so a parser that hard-codes the wrapper silently loses those messages; and a single malformed SentTime value should degrade to an undated message, not abort the archive — our first version failed a whole file over one bad timestamp.
There is one more trap worth knowing about if you ever parse one yourself: OLM writes timestamps as UTC but omits the zone suffix entirely, so a value looks like 2022-05-26T17:55:40 with no trailing Z. Read it as local time and every date in the archive silently shifts by your offset. We validated our reading of both the element semantics and the timestamps against an independent implementation before trusting it.
Because the format is a ZIP of XML rather than a proprietary binary database, an OLM is in some ways easier to read than a PST — the obstacle has never been technical difficulty, it is that only Outlook for Mac ever bothered. Windows Outlook will not open one, Apple Mail will not import one, and the commercial converters that fill the gap mostly want $40 or your uploaded mailbox.
- Container
- ZIP archive
- Per message
- One XML document (message_00001.xml …); parent directory = folder
- Addresses
- Structured attributes (OPFContactEmailAddressName / -Address), not header text
- Bodies
- OPFMessageCopyBody (plain) + OPFMessageCopyHTMLBody (HTML)
- Attachments
- Separate ZIP entries referenced by OPFAttachmentURL, with name / MIME type / Content-ID
- Routing headers
- None — no Received chain survives the export
- Timestamp gotcha
- UTC written with no Z suffix (e.g. 2022-05-26T17:55:40)
- Produced by
- Outlook for Mac only (File → Export)
- Opens in Windows Outlook?
- No — nor in Apple Mail or Thunderbird
Comparing formats? PST, OST, OLM, MBOX & EML explained — what each one is internally, and what is lost converting between them.
Before you trust a mail file to a website
Q. What is an .olm file?
The archive format Outlook for Mac uses when you export a mailbox (File → Export). It is Mac-Outlook-specific: Windows Outlook, Apple Mail, and Thunderbird cannot open it directly.
Q. Is my mailbox uploaded to a server?
No. The OLM is unpacked and parsed in a Web Worker on your own machine via the File API. You can disconnect from the network after the page loads and keep reading.
Q. Can I get messages out of the OLM?
Yes — read any message and export it as .eml for free. Batch export of whole folders or search results to MBOX/EML is part of the one-time Pro license.
Q. Do attachments work?
Yes. Attachments stored in the archive are listed on each message and can be saved individually, or extracted in bulk to a ZIP with Pro.
Q. Can I recover the original Received headers from an OLM?
No — and that is a property of the format, not of any particular tool. The message XML inside an OLM stores structured fields (subject, addresses, bodies, thread metadata) but no transport header block, so the Received routing chain is discarded when Outlook for Mac exports. Any .eml produced from an OLM therefore has rebuilt headers. If you need routing headers for forensics or deliverability analysis, work from the original PST/OST or the server copy instead.
Free to open, read, search, and export one message. Batch conversion is a one-time $19 licence — no subscription, no recurring fees.
Other formats & archives
Same local-first engine, every common mail format.