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Michael GreenFlag for Australia

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Outlook 2013 and 2016 .ost size limit - can it be increased above 50GB ?

I have a customer who has two senior managers that have huge mailboxes and insist that there should be no IT limitation on how much mail they need to keep.

My research indicates that Outlook 2013 and 2016 still have a limit for their .ost file of 50Gb.

Can this be increased ?  say to 100Gb ????

I found this which suggests its possible:
https://support.microsoft.com/en-us/kb/832925

but I would really like something more definitive that says what the real technical limitations are of the  .ost/.pst for Outlook 2013 and 2016 ????
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Scott C
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No, 50GB is the max.

A few months ago I was an Exchange Engineer for MS.  This question came up.  I went across the hallway to talk to the Outlook engineers and they said "no".  That is the limit.

Anything larger affects stability and performance.

If you could find a "hack" to go larger, you would be working in unsupported territory.

If you want "official" documentation, put in a call to MS, pay the $$ and they will send you something.
disable cached mode for these people
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Thanks - but the 50Gb limit still makes no obvious sense to me given these days of fast machines and ample memory and ample disk space.  is this limit a historical legacy of the file format ?  I seem to recall it was previously a 20Gb limit ?????
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Jackie Man
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You can disable the cache, but you will then increase latency and network traffic as all of the information will be going over the network all of the time.

You are correct, the previous limit was 20 or 25 GB.

As Jackie said, archive mailbox is the way to go.  And again, you do want to use cached mode for performance reasons.
I archive mail, have done for years, and that keeps the main mail file smaller.

It DOES make sense to have a limit because Outlook also has to perform well.

So please keep the limit as it is and archive older email.
Seriously, what do these managers have in their mailbox which risks filling more than 50Gb?

Standard text email, you're looking at kb, I won't bother working out how many messages it would need to fill 50GB. With an attachment you might end up in Mb, large documents, lets say 5Mb+, you would need 200 attachments to fill 1Gb; thats 10,000 attachments to fill 50Gb.

It is worth raising the question as to whether it is good management practice to use Outlook as a means of storing documents. I would say it isn't; save the attachment to the computer/network and if you need to keep the email you can remove the attachment from the email.
Hello,
If the windows Registry method is unable to increase the size then there is no other manual method that can increase the size of OST. If you are unable to store the entire data in OST,(since both the OST and PST serves the purpose for data files) you can split the respective PST files into smaller PST that will help you resolve your problem with storage.
I would suggest you a tool that will split-large sized PST which will split PST by size, date etc.

Hopefully, this will help to solve your problem with size.

Thanks & Regards,
Clark kent