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  Outlook-Google Synchronization by iCal4OL (via API)

FAQ English

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This is a guide for proper configuration of iCal4OL to synchronize Outlook with Google Calendar, Tasks and Gmail Contacts:

First of all, download the demo from the download page (or customer page) and install it.

There is also a version which can be installed without administrator rights (there is also a such full version).
Demo runs for 14 days. Prerequisites see here!
Then start iCal4OL..

The demo shows an entry screen, which is the only difference from the full version.
Click on the button [Start Program]..
Possible issues to this point see FAQ.

If you DO NOT intend to sync Exchange Public Folders or folders in different integrated *.PST files, do not mark on the tab "Options - Exchange/*.pst" the option:
[ ] Scan for Exchange Public Folders and in additional *.PST files, too
Please read about Exchange Support here in der FAQ.
For a large Exchange structure the first startup may take up to 15 minutes. All Outlook folders are scanned, which can be synchronized (calendar, tasks and contacts).

In the forum you will find additional topics about Google, e.g:

  • Important Notice for Google Calendar Sync
  • How to Sync 2 Google Calender with 1 Outlook Calendar (by Colorlabel/Category) (auch Deutsch)
  • Use Google Search with "iCal4OL Forum <question>"..

    iCal4OL offers many options to synchronize exactly as you wish. Initial Setup should be done with the Assistant on tab "Who".

    Alternatively Google Calendars can be synced by CalDAV v2!
    For this use the CalDAV Assistant [Others] and there:
    CalDAV example configuration (iCloud) see here.

    If you use manual configuration, please note:

  • Fullname (as on server): use the fullname field of your Outlook default email address (if different)
  • E-Mail (as on server): you MUST enter your email address

    (Those two fields are used to map attendee info to your Outlook identity..)
  • Your timezone: This field can't be empty. Do NOT modifiy the selected timezone rule

    First enter your Gmail address, then proxy if needed, and choose the HTTP-DLL:

  • WinInet.dll inherits the proxy settings of IE - Internet Options (not *.pac), does need a lot of CPU, does not support NTLM authorisation for proxy (and sometimes does not work at all).
  • WinHttp.dll needs less CPU and supports NTLM authorisation for e.g. proxies.
  • LibCurl.dll is the best choice, supports NTLM and can log HTTP traffic into Log.txt.
        Unmark "[X] Debug" (see tab "Options - HTTP_DLL" later on) if you don't need support!


  • Google Calendar API v3 needs OAuth Authentification (API v2 stopped working, see forum).
  • Daily access limit is 5000/request/users - about good enough to upload 3000 new events/day.
  • Use OAuth 2.0 Authentification (only possibility now).
  • You must first start your default Browser and you must login to the correct Google account!
  • As soon as you [Start authorization protocol for OAuth..], a new browser window/tab will open up, where you must grant access for iCal4OL.
  • After you copied back the "Verification code" into iCal4OL, you can continue with [Grant Access & Continue..].
  • Note: Some security software may prevent Copy&Paste. In this case double-click into field "Verification Code" to get it from the browser. Typing it manually may be not easy, due to similar 0,O (null,Ohh).
  • If [Start authorization protocol for OAuth..] is disabled, OAuth 2.0 may still be valid (from a previous config). Just click [Grant Access & Continue..].
  • If you get an error after [Grant Access & Continue..], OAuth 2.0 is not valid anymore. Click [Revoke] and redo the authorisation protocol.

    Now the Google (Sub-)Calendars will be listed. The assitant supports now nine Google Calendars.

    If this is not working, there is a network issue. There are unfortunately many possibilities for this.
    Perhaps you copied back the wrong verification code (email address must correspond to account!), or the HTTP-DLL from section 1) does not work correctly.

    1. A firewall (of OS or of an antivirus security package) might be active. You must allow iCal4OL to connect to the internet.
    2. A proxy may be active. If a proxy is configured in Internet Explorer under Internet Options, add those settings on tab "Options- Proxy". But *.PAC configuration files (JavaScript) are not supported by iCal4OL. Download and analyze *.pac file in a browser and identify the actual proxy in it. Enter the proxy on tab "Options-Proxy" manually, save Default.ini and restart the assistant.

    3) - 6)
    The configuration for the other sections should be clear. Please reed the tooltips!

    The splitting by Outlook categories of events into different Google Calendars is only something for specialists. You should know what you are doing ;-)

    If multiple calendars syncs must be configured by the assistant, multiple configuration files (*.ini) will be created automatically. You will see those later on tab "Run" chained together, because only one Calendar Sync can be configured per .ini file.
    Want to know more about this? Read the FAQ ;-)

    Before you start the first sync on tab "Run" - Optimization:

  • iCal4OL stores for new installations (>=2.12.15) the Sync Fields not anymore as userdefinded MAPI fields (e.g. in Outlook.pst).
    This was not optimal for Exchange environments (the printout in memostyle will show those fields, even for attendees)!
    Older installations of iCal4OL can be re-configured, to use an external DB for the Sync Fields (see screenshot below).
    In this screenshot, the folders are "monitored" for deleted items. Actually, it's only recommended to use it for newer Exchange/Outlook 2013.
    Without those options, only the "Deleted Items" Folder of Outlook is used for detection of deleted items, which in most scenarios is sufficient!
    Read tooltips and see also this FAQ article!

  • I advice NOT to upload Birthday and Anniversary Events (of Contacts).
    The reason here is the (unbearable) behavior of some Outlook installations: a Contact Change often produces as a duplicated birthday event!
    This can be prevented by an export filter: /(Birthda.*|Annivers.*)/ or /([A-Z,a-z,\ ]*\'[s]\ Birthday)/,
    or in German Outlook: /(^Geburtsta.*|^Jahresta.*)/
    (On tab "Maintenance" it is possible to get rid of duplicates.)

    Importfilter is on tab "1.1 More" (activate enhanced options on tab "1. How"):

  • In Outlook generated Public Holidays may cause sync issues!
    If this Outlook option was active, you may want to change before first sync on tab "1. How", the selected time period rule to -31 to +365, or perhaps better, activate the enhanced options (1.How) and on tab "2.1 More - Export" enter the category filter -Holiday", to exclude them for upload. Reasons:
    - Google has a public holiday calendar, too.
    - Those events may be defective, resulting in sync issues (ScanPST.exe may help).
    - First sync is very slow.

    The main configuration tab "1. How"

    • Select the time period. The past is gone. Default is "from -31 days on (incremental)".
    • Read the tooltip of the options. Most options are explained in the Online Documentation.
    • Use button [Tasks Sync] to configure Google Tasks Sync (see below).
    • Every Google Calendar has a unique UserID. The Primary Google Calendar does use the Gmail Email Address (and therefore UserID is empty). Best, use this Calendar UserID on tab "Who" as Email (done by Assistant and [Choose Google Calendar] automatically).
    • If you run in deep trouble, because you used in the Google Browserinterface the button [Delete] for the Primary Google Calendar, you have two possibilities to fix it:
      1. Select 1-Way-Upload (What); Activate enhanced options (1.How); [X] Re-upload previous deleted events (2.1 More)
      2. [Choose Google Calendar] and use [Undelete]...
      3. On tab "Sync Fields" you can force all elements of a folder to modification time NOW(). They will get uploaded (=undelete), even if previously deleted in Google.

  • At the bottom you can activate additional Enhanced Options (perhaps already done by Autoconfiguration) on tab "1.1 More - Import" and "2.1 More - Export".

    Meeting Invitations - Important:

    If you sync a Smartphone by CalDAV with the same Google Calendar..
    Google CalDAV API has "calendar-auto-scheduling" turned on. A modification of an invitation by CalDAV (but not by API v3) will trigger an Email invitation from Google!

    Therefore I advise, not to upload attendees at all.
    Note: Suppressing attendees is default in the assistant for Google Calendar API v3 (tab "Who"), but can get deactivated.

    Manually: On tab "2.1 More - Export" click first on [Default] to reset everything here. Then mark the option [X] Suppress attendees (...):

    In addition (if not yet set) you can activate on tab "Google" to upload attendees in the event description.

    Google Task Sync must be configured manually!

    There is a button for it on tab "1. How".
    See Doc Google Aufgaben Synchronisation (Google Tasks Sync / GTask Sync)

    The Contact Sync must be (re-)configured, too!

    Important: under CONTROL PANEL - Phone and Modem Options - Location .. enter the correct area code, or even better use "International Freephone Service"!
    Otherwise the plus sign in front of a phone number may be ommitted during download sync = Outlook Issue; e.g. +41 893..

    See tab "Contacts"... Gmail Contacts Sync.
    You may want to start this first separately here (or test it with "[X] Simulation" for analysing the LOG.txt). Read the tooltips of the options, too!

    Now, the first interactive Sync is due. Go on tab "Run" and save the configuration (Default.ini).

    After the sync look into LOG.txt. If there was an error during the sync, it will be written into the LOG.txt and the backcolor of the counter frame (read,skipped..) is red.

    To Sync automatically in the background, for example when you logon to your machine, can be configured directly in the assistant from 2.13.6 on.

    Here the description, if you need to do this manually (with some additional settings):

    Now look under START - All Programs - iCal4OL .. Many shortcuts (links) are available to start iCal4OL, e.g. directly in background.
    All background syns possibilities are explained here.

    In Windows 8, the Start Menu is not docked anymore. Therefore enter in the address field of an explorer window:
    Version with admin rights: C:\ProgramData\Microsoft\Windows\Start Menu\iCal4OL\
    Version without admin rights: %APPDATA%\Microsoft\Windows\Start Menu\iCal4OL\

    Perhaps you first want to fine tune on tab "Options - Startup (General)", if Outlook should be opened together with iCal4OL, and if syncs should pause (or end) when Outlook gets closed.

    You may want to copy such a link to your STARTUP (AUTOSTART) Folder or on your DESKTOP (Drag&Drop with right mouse button and choose "Copy" or "Make a link"):

    That's it! Please read the FAQ, too. Everything is explained somewhere (see Doc, and some details are in the forum).

  • MS-Outlook® ist eingetragenes Warenzeichen der Microsoft Corp.,   iCloud® ist eingetragenes Warenzeichen der Apple Inc.
    iCal4OL © ical4ol [at]