Problem solutions

Applies to version: Version 4.x, Version 5.x, Version 6.x

If you have difficulties with SimpleSYN, read the following information.

Question / ProblemSolution

SimpleSYN does not establish a connection, the symbol in the Windows® notification area is shown grey

If SimpleSYN cannot establish a connection make sure the following is correct:

  1. Make sure SimpleSYN is installed and started on both the client and the server computer
  2. At least one computer has to be configured as SimpleSYN server and a second as SimpleSYN client
  3. Install the latest version of SimpleSYN on all computers that are to be synchronized
  4. Make sure you have an active internet connection on both computers
  5. Check whether the Windows time and Windows timezone is correctly set on both computers. Set the same time/timezone on both computers.


  1. Make sure the correct server has been selected on the SimpleSYN clients.
  2. Make sure the password has been entered correctly.

No synchronization is taking place

Make sure that you have selected the Outlook® folders for synchronization in the synchronization settings on the client PC.

More information can be found here.

The synchronization settings of the SimpleSYN-client only show “No folder information is currently available” under “Server Folders"

This message is being shown if the SimpleSYN-client cannot establish a connection to the SimpleSYN-server or if the SimpleSYN-server is not available. Make sure SimpleSYN has successfully established a connection between server and client. Right click the window of the server folders and click “Refresh”.

SimpleSYN is not being started automatically

Activate under the menu point “Options” the checkbox “Start with Windows”. More information can be found here.

E-mail duplicates occur when synchronizing

Duplicate e-mails can occur when e-mails from more than one computer being synchronized are retrieved from the e-mail server. This is the case if the function “Leave copy of messages on the server” was activated in a POP3 E-mail account.

In this case deactivate the Outlook function “Leave copy of messages on the server” so as not to save e-mails in your mail server and download them repeatedly.

To deactivate this function follow these steps:

  1. Open Outlook
  2. Open the Backstage area by clicking on “File
  3. In the category “Information” click on “Account Settings” and “Add or Remove Accounts…
  4. Highlight the POP3 E-mail account in question and click on “Change
  5. Click on “More Settings
  6. In the tab “Advanced” deactivate the check box “Leave copy of messages on the server “ 
  7. Confirm the changes by clicking “OK“ 
  8. Click on “Next“ and then on “Finish

Should this feature be necessary other solution possibilities exist:

  • Disable automatic synchronization of SimpleSYN, fetch the e-mails on both computers and manually synchronize SimpleSYN afterwards
  • End SimpleSYN before fetching the e-mails and only restart SimpleSYN after both computers have fetched the e-mails.
  • Set the E-mail account up so that e-mails are retrieved by one computer and sent from another one

Initial synchronization leads to duplicates of tasks, contacts or dates

If SimpleSYN apparently duplicates tasks, contacts or dates during the initial synchronization these have as a rule been created manually beforehand and therefore different for SimpleSYN. Usage of other synchronization tools may also lead to duplicates during the initial synchronization of SimpleSYN.

Delete the doubled items. All further synchronizations won’t create duplicates

Some conflicts cannot be solved

If a conflict occurs during automatic synchronization and the target folder settings are being modified before the conflict is solved it may happen that the conflict cannot be solved anymore.

In this case synchronize once manually into the same folder as before to allow conflict solution. To do this open the according folder in Outlook® and click on the button “Synchronize Folder to” in the SimpleSYN toolbar. In the following SimpleSYN dialog select the previous Outlook® folder as target for the synchronization. The Outlook® folders used during conflict occurrence are shown in the conflict overview.

Already solved conflicts can be hidden from the list. More information can be found here.

The SimpleSYN toolbar is not being shown in Outlook®

Check whether the SimpleSYN Add-in has been deactivated by Outlook®. Open Outlook® and follow the instructions.

Outlook 2010 and newer:

  1. Open Outlook
  2. Check whether the SimpleSYN menu strip was switched off. To this end click in Outlook on “File” to open the Backstage area and then on “Options
  3. Click in the area “Categories” on “Customize menu strip
  4. In the area beneath “Customize menu strip” click on “Main tabs” and search for the entry “SimpleSYN“
  5. Check the check box next to the entry “SimpleSYN

If no entry “SimpleSYN“ is to be found under the main tabs then proceed as follows: 

  1. In the Outlook Backstage area click on “Options
  2. In the area “Categories” click on “Add-Ins
  3. Search for the SimpleSYN Add-In in the detail area in the list of disabled items

If the SimpleSYN-Add-In is listed in disabled items, then follow these steps:

  1. In the tab “Manage“ click on “Deactivated elements“ and then on “Go to
  2. Highlight the SimpleSYN Add-In and click on “Activate
  3. Click on “Close
  4. Shut down and restart Outlook

If the SimpleSYN toolbar is still not visible:

  1. Click in the Outlook Backstage area “Options
  2. In the area “Categories” click on “Add-Ins
  3. Search for the SimpleSYN Add-In in the detail area in the list of disabled items
  4. In the tab “Manage“ click on “COM-Add-Ins“ and then on “Go to
  5. Check the check box next to the disabled SimpleSYN Add-In in the dialog COM-Add-Ins
  6. Click on “OK
  7. Shut down and restart Outlook

The notification “Some folders could not be synchronized” is shown

This notification appears if the target folder for the synchronization of one or several folders is not available. This can have several reasons:

  1. The available folders have been restricted. More information can be found here
  2. New folders cannot be created. More information can be found here
  3. The data store is currently not available.

Click on the notification to show the not synchronizeable folders. Here it is possible to specify how to handle the unsynchronized folders. Click on “Do not synchronize this folder” to not show the notification again

The error message “An error occurred during access of your Outlook data is shown

This message can be caused by faulty Outlook® Add-Ins of third party producers. Faulty Add-Ins of third parties can affect the closing of Outlook® which may leads to locking of the Outlook® PST file. This prevents communication between SimpleSYN and Outlook®.

In this case deinstall the faulty Add-In, contact the support of the producer or wait for an update.

The message can also occur if your PST file is corrupt. More information about checking the PST files can be found under:

The error message “Authentication failed” is shown

Open SimpleSYN on your “SimpleSYN server” and click on “Synchronization Settings”. Click on “Manage Users” to open the SimpleSYN user management. Please make sure, the user account “All users” is activated. Afterwards click on "Options" and enter a password for your SimpleSYN server. Don't forget to save the settings with a click on "Save".

If you are done with your SimpleSYN server open SimpleSYN on your “SimpleSYN client-computer” and click on “Options”. Make sure, that the Logon is set to “default” and please make sure, you have the correct Password from your server computer entered in the field “Password”.

Also make sure, that the Windows clocks on both computers are set to the same time, date and time zone.

More information can be found here.

I get the error message "Either there is no default mail client or the current mail client cannot fulfil the messaging request. Please run Microsoft Outlook and set it as the default mail client""

Please make a Outlook repair installation on this computer. Please follow this instruction:

Important: choose a full online Outlook repair installation and NOT a quick repair.

I get the error message "SimpleSYN could not establish a MAPI session"

Please follow these steps:

  1. Select the right Outlook version in SimpleSYN main window under "Options -> Advanced Options > Outlook version". Save the settings and restart SimpleSYN

If the behavior still occurs:
Uninstall SimpleSYN and reinstall SimpleSYN.

I cannot synchronize the Outlook categories

Provided you have made changes to the default settings of the color categories, you will have to manually set up the list of color categories (formerly main category list) identically on all computers. The category list is not synchronized by SimpleSYN. The assigned categories in the items, however, are kept and synchronized by SimpleSYN.

The read state of an e-mail was not synchronized

The behavior may e.g. occur when an e-mail has been opened and at the same time the reading status of the e-mail is changed on another computer or if SimpleSYN has been issued to one of the PCs while the reading status changes. If the item or another item in the same folder is changed and synchronized again in the future, then the current read state is also taken over again. There must be an actual change (for example, assignment of a category) for Outlook (with a change of the date), but a new change of the read state does not represent a direct change for Outlook because the date is not changed here.

I can not install SimpleSYN. I get the message that Outlook is not installed. But Outlook is installed, it's Office 365.

In that case, you probably have an Office 365 version from the Microsoft App Store installed.

Programs from the Microsoft App Store can not currently recognize SimpleSYN (these programs are isolated from the rest of the system).

Please reinstall Outlook / Office at

Then everything should work and go through the installation.

On the client PC, folders are not displayed under the "Synchronization Settings" even though the client PC and the server PC are connected. The folder list is empty.

Please follow these steps:

  1. Select the right Outlook version in SimpleSYN main window under "Options -> Advanced Options > Outlook version". Save the settings and restart SimpleSYN.
  2. Make sure neither Outlook nor SimpleSYN is started with administrator rights.
  3. Check if SimpleSYN and Outlook are using the same Outlook profile. You can see the Outlook profil in SimpleSYN in the main window > Options
  4. Make sure SimpleSYN is not started with compatibility settings enabled. To check this, right click on the SimpleSYN shortcut and select “Properties”. Click on “Compatibility” and remove tick in the checkbox “Run this program in compatibility mode”. It is possible, that this setting was somehow enabled during the Windows 10 upgrade.

SimpleSYN Version 4 can not be started anymore. After a "double click" on the SimpleSYN link, SimpleSYN will not be loaded

In this case there is an problem on the file "SimpleSYN.config", so SimpleSYN can not be started anymore.

To repair SimpleSYN on this computer, please follow these steps:

  • Open a Windows Explorer and navigate to this directory:

    For Version 4:

  • In this directory you will find the file: “SimpleSYN.config” (may also be shown as just “SimpleSYN” without the extension .config).
  • Delete this file
  • Restart SimpleSYN

Then SimpleSYN starts normally again. You would then need to activate SimpleSYN only once with your license file.