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How does Olminator work?

Why Olminator at all?

Microsoft Outlook for Mac is one of the very popular, very powerful and hence heavily used applications in the Microsoft Office suite of applications.

Over the years, being one of the many Microsoft Outlook for Mac users, you may have accumulated a large amount of emails in your inbox, appointments in your calendar or contact cards in your contacts section in Microsoft Outlook for Mac. You may even have kept old emails locally on your computer (Microsoft Outlook for Mac supported locally stored files for a long time) and this "archive" of yours has been constantly growing over the past years. Now for some reason you've decided that you want to switch your email client or your calendar application, or you want to take your contact cards to some alternative app, and wonder how to get those thousands or hundreds of thousands of entities out of Microsoft Outlook for Mac?

This is what Olminator will help you with.

Like many other applications, too, Microsoft Outlook for Mac uses a proprietary format to store the data it handles. While this may improve the functionality available or performance possible, it makes moving your data from Microsoft Outlook for Mac to other email, calendar or contacts applications harder – but not impossible.

To export your email, calendar, contacts or notes information (among the other content types supported) Microsoft Outlook for Mac allows you to write all of it into a .olm archive file. While this file's inner working/format are not officially documented and hence may change at any time in the future, we're lucky enough that it is actually not more than a huge zip-compressed file containing a bunch of XML files. zip-compressed files we know how to handle and in regards of XML files one can say that they are to the largest part self-explanatory and can be "re-engineered" in those less self-explanatory places by running a sufficiently large test data set through the export process. Once we've understood the .olm file format, we can create conversion tools that turn this format into whatever alternative file format we prefer. This is what Olminator does. And that's what many other .olm conversion tools available do, too.

If you don't know how to export an .olm archive from "Microsoft Outlook for Mac", you'll find a step-by-step documentation here at Exporting your data from Microsoft Outlook for Mac.

Hint: If you're bored and want to take a look into the .olm file format yourself: unzip an .olm file by double-clicking it in Finder – this will cause the file to be "unzipped" into an equally named folder in the same directory as the .olm file. You can then browse the contained folder structure and examine the various XML files with TextEdit or your preferred XML viewer/editor. No magic anywhere.

See Olminator in action on YouTube

For those of you who don't want to read all the documentation or who like to get an initial idea about the entire procedure, I have recorded a video and published it on YouTube. It explains the entire process, showing you how to export your Outlook for Mac items, convert them using Olminator and importing the conversion results, i.e. your emails, calendar or contact items, into the respective Apple productivity apps like Apple Mail. Here's the link to the video: https://youtu.be/gx3963i55Yc

How does Olminator work?

The conversion of emails, calendar entries and contact information into formats digestible by other applications takes place by reading a so-called ".olm" file which Microsoft Outlook for Mac can export. Olminator then creates corresponding file formats for emails (.mbox or .eml), calendar events (.ics), contact information (.vcf) and notes (.html) in the conversion process and places them into your file system. Given your email, calendar, contacts or notes application of choice support those conversion file formats, you can then import the respective content.

Since v2.20 Olminator also supports bulk-converting all the above mentioned content types into PDF files, which is one of the most commonly supported file formats across platforms. If you only try to "preserve" those Microsoft Outlook items for being able to access, print, share or search their content for decades to come, PDF may be worth a consideration, too.

The conversion process keeps the folder structure in place in which you have organized your Microsoft Outlook for Mac inbox. This will ensure that after importing your emails, you'll find them in the respective subfolders in your inbox of your email application.

Caveat: Olminator does only convert .olm files (the file format produced by Microsoft Outlook for Mac when exporting inbox). It does NOT convert .pst files (the file format produced by Microsoft Outlook on Microsoft Windows)!

Once the conversion is completed, Olminator will have placed the following entities into your computer's file system into the output folder you have selected for the conversion:

  1. Subfolders: For each account you have configured in Microsoft Outlook for Mac a subfolder with a corresponding name can be found. Within those account folders you'll find folders for emails, calendars and contacts with their respective names. Within the emails folder, you'll recognize hierarchy of your Microsoft Outlook for Mac inbox folder structure. For each inbox subfolder,
  2. .mbox/.eml files: .mbox and .eml files follow RFC822. .mbox files contain your converted emails of the corresponding inbox subfolder - they are basically a sequence of .eml entities in a single file. If an .mbox file grows too big and you've configured a limited maximum size for an individual email output file (the default defined in Olminator is 2GB), you may find several .mbox files with the same name prefix and a consecutive sequence number. Each of the files belongs to the same email inbox folder (hence the same name prefix), but only contain a portion smaller than you configured size limit in content. Some email clients seem to put a limit on the maximum file size they can import successfully. Cutting the email content into appropriate chunks works around this problem. You can either import individual.mbox files into e.g. Apple Mail, or select any folder (e.g. the output root folder) so that all .mbox files get imported in a single step.
  3. .ics files: .ics files contain calendar information in a portable format (RFC5545). This format is supported by a number of Calendar applications, as it is by Apple Calendar. Some Microsoft Outlook for Mac functionality may not be supported by other Calendar applications or the .ics file format (RFC 5545). Those non-standard features hence can't be converted and are lost in the conversion process. Nevertheless, all relevant information is converted properly. This includes recurring event information with individual event exceptions (e.g. changed times/dates, changed titles/participants, deleted individual event occurrences in a recurring event series). Timezone information is preserved (e.g. if appointment times where specified in a specific timezone), as are attachments.
  4. .vcf files: .vcf files contain contact information in a portable format. This format is supported by a number of Contacts applications, as it is by Apple Contacts. As of v2.50 of Olminator, you can also convert contact information into CSV (Comma-Separated Values) format which can be post-processed in Apple Numbers, Microsoft Excel and many other applications.
  5. .html files: .html files are generated for notes information as a portable format. Your browser can display those files and Apple Notes can import them as well. As of v2.40, you can also convert all other item types into HTML, not just notes items.
  6. .pdf files: Olminator also allows to bulk-convert all email, calendar, contacts and notes items to PDF or HTML alternatively. This will not allow you to import those files into the before-mentioned productivity applications, but those are great formats for archiving, indexing/searching, printing or otherwise sharing with someone.
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