MDaemon Calendar.mrk, AddrBook.mrk & HIWATER.MRK Files – An Abstract View

by Admin
March 16, 2016

What is MDaemon, its file system and how they relate to each other?

MDaemon is a Windows operative shareware email and instant messaging server, which is the product of ALT-N Technologies. By default MDaemon’s store location is : C:\MDaemon\Users\

(where is the domain name, which contains all the users’ accounts data and may vary accordingly)

When a particular account is further opened, a list of folders, all having .IMAP and a few .msg files are displayed. When any of these .IMAP folders, say Contacts.IMAP, is further accessed, the list of files that gets displayed is in .mrk format :


Know More about MRK and MSG files?

MSG is an email storing file format, which includes a header and email message body, appearing in plain text. The header contains all the sender’s and recipient’s details and the message body contains all email content, images, attachments, hyperlinks, all in plain text.

Just as MSG have their significance (due the message information they contain), similarly MRK files are crucial too. HIWATER .MRK comprises of all the account’s details : subscription of IMAP folders, access information of POP/IMAP emailing services, public folders availability, information about last access, mail rules and so on.

About WorldClient

WorldClient is a browser based mail client, which provides users with the facility to access all their MDaemon messages, calendars, address book, notes etc. Users just need an internet connection to access all their data, irrespective of where they are located. WorldClient stores all the emails, notes, contacts, tasks, calendars, documents etc. in .mrk, one .mrk file per data item, which is saved in their corresponding parent .IMAP folder. All these IMAP folders are stored in one single root folder, which corresponds to a particular user account.

The IMAP folder, when opened, comprises of a list of files: *.mrk, *.msg. For example, Contacts.IMAP folder contains these files: AddrBook.MRK, Imap.mrk, HIWATER.MRK and a number of .msg files. Each .msg file will have information about a single contacts. Thus, if user account has 20 contacts, there will be 20 .msg files, each containing information about one contact.

Likewise, the following IMAP folders will contain the following files :

1 – IMAP: Calenders.mrk, Imap.mrk, HIWATER.MRK, .msg files

2 – IMAP: notes.mrk, Imap.mrk, HIWATER.mrk, .msg files

3 – Tasks.IMAP: tasklist.mrk, , Imap.mrk, HIWATER.MRK, .msg files

All these folders have their individual HIWATER.MRK file, which contains all the information, pertaining to that particular IMAP folder. Every IMAP folder has their own set of .mrk files and .msg files, containing all the information, related to them.

What data is stored in AddrBook.mrk, Calendars.mrk?

WorldClient recognizes only .mrk files and fetches all its data from their corresponding .mrk files, like it manages all its contacts data from AddrBook.mrk, notes from Notes.mrk, calendars information from Calendars.mrk etc.

Outlook, on the other hand recognizes only .msg files. It reads these .msg files from their particular IMAP folders and manages all the data accordingly.

What is Connection between these .mrk and .msg files?

Consider a situation, where you have inadvertently deleted your AddrBook.mrk file. Not only this, all the contacts are deleted from WorldClient. When Outlook is synchronized using Outlook Connector, all the contacts will be automatically deleted from Outlook too. Yes, even the .msg file will also get deleted, once the contacts are gone from Outlook.

Note: MDaemon can’t do without AddrBook.mrk file and once deleted, it automatically creates its new copy, without any data in it.

Once the backup of AddrBook.mrk file is restored, all its contacts appear under <contacts></contacts>


It can be seen that the contacts are there in AddrBook.mrk file, but still there is no .msg file seen in Contacts.IMAP folder.

Once Outlook is again opened, it will restore all the contacts from the data stored in the AddrBook.mrk file. And as soon as the contacts are restored in Outlook, their corresponding .msg files will also get created, in the Contacts.IMAP folder, at MDaemon’s store location :


The same thing holds true for other IMAP folder too – Tasks.IMAP, Notes.IMAP, Calendars.IMAP. Each reading its data from their corresponding .mrk file and creating their related .msg files, when Outlook is synchronized with MDaemon, via Outlook Connector.

How to view MDaemon Data in Outlook, without relying on Outlook Connector?

One of the major drawbacks of viewing MDaemon data (Mailboxes, Calendar, Address Book, Task, Notes) in Outlook with Outlook Connector is that, Outlook becomes completely dependent upon MDaemon for managing its data. When some crucial data goes missing from MDaemon, unfortunately it gets deleted from Outlook also.  So user may need to access all their MDaemon data without being dependent on any connector. But “How to Export MDaemon Mailbox to PST” remains a big question.

MDaemon Converter: Solution Par Excellence

This is the perfect solution here as the software not only supports bulk conversion of MDaemon mailboxes to Outlook (by saving them in PST format) but also allows the MDaemon data to be converted in 8 other files formats: MSG, MBOX, PDF, EML, EMLX, HTML, RTF, MBX. Once converted in desired format, the MDaemon mailboxes can be easily accessed and used in multiple applications like : Thunderbird, Apple Mail, Windows Live Mail, Outlook Express, The Bat!, Entourage, web browsers, Acrobat Reader, office documentation, forensic analysis etc. The software offers precise and reliable migration of MDaemon Data (Mailboxes, Calendar, Address Book, Task, Notes), which allows migration of MDaemon data without damaging or altering anything in the source and resultant data.