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Choosing Between Outlook 32- or 64-bit

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› Outlook › Choosing Between Outlook 32- or 64-bit

Last reviewed on February 15, 2021     27 Comments

A popular question on many forums goes something like this

Outlook isn't recognized by [application_name]. The error is "Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default client." When I check the Default Programs, Microsoft Outlook is the default for everything.

First and foremost, when you receive this message while using Outlook 64-bit, try the 32-bit version of Office. While some applications and addins work with the 64-bit version, not all do. Unless you need to open large (2 GB) Excel and Access files, you won't benefit the 64-bit version. Wanting to use the 64-bit version because you use a 64-bit operating system isn't enough reason to use it, if you need compatibility between different applications, you'll need to stick with the 32-bit build.

Repeat: Avoid the 64-bit version unless you have confirmed the add-ins and utilities you want to use will work with it. There is no benefit to using the 64-bit version for typical users - Office is not going to run faster or better. Only those who work with huge (2GB) record sets and spreadsheets need the 64-bit version. The 32-bit version works fine on 64-bit Windows (do not use compatibility mode).

While many applications will work with the 32-bit version of Outlook, some programs will need to be updated before they will work with Outlook 32-bit. This is normal with all new versions of Office.

Note: If you are using an Office 2013 or newer Click to Run suite, add-ins should work with it. some add-ins may need to be updated, but Office or newer applications can run addins. This is the exact opposite of Office 2010 Click to run!

If you sync with a smartphone or pda, you need to confirm your device will sync with the 64-bit version of Outlook.

From Microsoft:

Office provides support for the 32-bit version of Office programs running on 64-bit operating systems by using WOW64, a compatibility environment provided by the operating system that allows a 32-bit application to run on a Windows 64-bit operating system. Using the 32-bit version of Office allows people to continue to use existing third-party add-ins for Office that are 32-bit. The 32-bit version of Office is the recommended option for most users, because it prevents potential compatibility issues with other 32-bit applications, specifically third-party add-ins that are available only for 32-bit operating systems.

Pros & Cons: 32-bit

  • Many existing add-ins and programs work with it.
  • Can co-exist with other 32-bit Office applications.
  • Office has the same memory requirements as Office 2007 but even with 32-bit Office, you can open, edit, and switch among applications much faster on 64-bit Windows than on 32-bit Windows.
  • Syncs using WDMC

Pros & Cons: 64-bit

  • Supports larger file sizes - over 2GB in Excel and Access
  • Most add-ins and Active X controls do not work with it
  • Cannot co-exist with 32-bit Office family applications
  • Syncing with Windows Mobile devices using WMDC NOT supported

"Click to Run" version

While the click to run Office suite is 32 bit, most add-ins will not work with it because it runs in a virtual space. Users need to install a regular 32-bit suite instead. I don't recommend the Click to Run version, except for users who need two versions of Outlook.

More Information

64-bit editions of Office (TechNet)

Choosing Between Outlook 32- or 64-bit was last modified: February 15th, 2021 by Diane Poremsky

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About Diane Poremsky

A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

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Evets Nedrow (@guest_204978)
March 2, 2017 3:09 pm
#204978

Thank you, Diane. One quick question -- will the Outlook profiles of our 80 users need to be rebuilt? We're going from Office 2013 64-bit to Ofc 2013 32-bit. Thanks again --

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Diane Poremsky(@diane-poremsky)
Author
Reply to  Evets Nedrow
March 6, 2017 12:31 am
#205048

No, they won't lose anything in their profile, not as long as you are using either the same version or are moving up to the next version.

If you downgraded from 16 ro 13, then you would need to make new profiles.

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Chris S. (@guest_202462)
October 21, 2016 10:00 am
#202462

I am trying to install Business Contact Manager for Outlook 2013 x64 ( only 64 and 86 bit available), however I am running Office 2010 x32. Any ideas on how to get BCM to work??

Thank you.

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Diane Poremsky(@diane-poremsky)
Author
Reply to  Chris S.
October 29, 2016 1:07 am
#202618

You need to use the x86 version of BCM with 32-bit Outlook. (32bit is the same as x86).

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nahrafqifahs (@guest_192225)
July 30, 2015 8:49 pm
#192225

Thank you! Just what i'm looking for. Aid4Mail working fine with 32-bits MSI, MAPI Issues. That why i'm reinstalled with 32-bits.

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hugopoelen (@guest_191674)
July 1, 2015 3:18 pm
#191674

Same situation today. I start in the safe mode. It works for a while, than the ventilator starts revving up and Outlooks is going to restart. but after a restart it comes back in the default settings.

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Diane Poremsky(@diane-poremsky)
Author
Reply to  hugopoelen
July 2, 2015 1:28 pm
#191700

The antivirus addins are disabled in Outlook? Look in the event viewer and see if it gives you any clues as to what mightbe triggering it.

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hugopoelen (@guest_191653)
June 30, 2015 3:59 pm
#191653

Diane,
It had started Outlook in Safe mode (outlook.exe /safe). It started OK. I could use it to send some messages and reply. But later (I did not use it at that moment) it crashed and restarted again.
I am a bit lost

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hugopoelen (@guest_191636)
June 30, 2015 9:43 am
#191636

Diane,
Thanks for your fast response.
Could it be that the problems coincide with the change of Virus killer from Norton to ESET.
I have been in the Safe mode sometimes lately and switched of all active add-ins, But it went on after I tried to use the normal set-up. Now I will check the Safe mode again.

Thanks
Hugo

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Diane Poremsky(@diane-poremsky)
Author
Reply to  hugopoelen
June 30, 2015 12:21 pm
#191641

possibly. Is the ESET addin enabled in Outlook? Disable it.

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hugo Poelen (@guest_191629)
June 30, 2015 4:47 am
#191629

OOOPS
Must be
I have a 6 pst files linked to Outlook 2013
They are 3.8 Gb, 4.9 Gb, 1.2 Gb and 2.1 Gb and 492 Mb

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Diane Poremsky(@diane-poremsky)
Author
Reply to  hugo Poelen
June 30, 2015 8:09 am
#191630

The pst file sizes indicate you are using Unicode for at least some pst - if the smaller pst files were created by Outlook 2010 or 2013, they are definitely Unicode as well. Unicode pst were introduced in Outlook 2003 and were the default pst format since them - they can grow to 50GB or more (20 to 50GB is the recommended max).

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Hugo Poelen (@guest_191626)
June 30, 2015 4:18 am
#191626

Hi Diane,
I am looking to solve my problems with Outlook 2013. since a few months I am struggling to keep it alive ;-). When I start a new email the cpu starts speeding up. And if I am a bit unlucky it stops and starts flashing and finally restarts.
I have a few large pst files collected over the years. I am using SCANPST to repair them nowadays regularly. Therefore I thought that I might run up against the 32-bit threshold.

Any suggestion??

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Diane Poremsky(@diane-poremsky)
Author
Reply to  Hugo Poelen
June 30, 2015 8:13 am
#191631

It only happens when you start writing an email? I assume it also happens for replies? Do you leave Outlook open all the time? (You should.)

Does scanpst find errors? I would stop running it routinely, only run it if outlook tells you to. If it finds errors that need fixed, you need to find the cause, not treat the symptoms.

Does outlook work better in Safe mode? If so, this means one of the support files or addins is causing the problems.

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