Microsoft is migrating all Outlook.com mailboxes to new Office 365 Exchange Online mail servers, accounts will be moved starting Q1 2016 in the USA. The migration of other countries is targeted to be completed by the end of 2016.
There are major differences between OST and PST containers for you emails. PST files are used to download all your emails so you can make a full back-up, OST is only a recent used cache of emails. You can read full details here.
But to summarize the primary differences between the two types of Outlook data files are as follows:
Outlook Data Files (.pst) are used for POP3, IMAP, and web-based mail accounts. When you want to create archives or back up your Outlook folders and items on your computer you can use (.pst) files.
Your items can also be moved or archived to an Outlook Data File (.pst). Because a .pst file is kept on your computer, it is not subject to mailbox size limits on the mail server. By moving items to a .pst file on your computer, you can free up storage space in the mailbox on your mail server.
You had the potential to move all you emails into (.pst) file and make a full back-up of your emails.
Outlook Data Files (.ost) are used when you have an Exchange account and want to work offline or use or use the default Cached Exchange Mode. Outlook Data Files (.ost) are always copies of items that are saved on a mail server and don't have all of your emails downloaded like a Outlook Data Files (.pst), but only recent items are cached to facilitate synchronization.
When you work offline, folders that are synchronized are determined by Send/Receive groups. By using Send/Receive groups, you can choose which folders are synchronized and kept current so that when a connection to the server is not possible or you choose to work offline, you can continue to work with those items. You can also specify that updates to the Address Book be downloaded during synchronization.
You can configure Outlook to keep a local copy of your items on your computer in an Outlook data file that is named an offline Outlook Data File (.ost). This allows you to use Cached Exchange Mode or to work offline when a connection to the Exchange computer may not be possible or wanted.
With Cached Exchange Mode, you do not have to set up Send/Receive groups, choose folders that you want to be available offline, and then keep those folders synchronized.
The .ost file is synchronized with the items on the server that runs Exchange. Because your data remains on the Exchange server, you can re-create this .ost file on your new computer without having to back up the .ost file.
How can you tell your mailbox has been migrated?
What are the negative affects of this migration?
- First sign you have migrated is your Outlook Hotmail Connector Version 14.0.6123.5001 will stop syncing. They have ditched support for the Hotmail Connector, which implies no more PST files, now you are forced to use a OST file. OST files do not contain all you emails, its just a cache so you cannot back up all your full emails anymore. You cannot copy a OST file and expect a full back-up.
- Disappearing or Missing Folder in Outlook
During the migration, none of the folders are being replicated. I lost all my folder structures and rules.
Office 365 Exchange Online now uses OST vs PST file?
There are major differences between OST and PST containers for you emails. PST files are used to download all your emails so you can make a full back-up, OST is only a recent used cache of emails. You can read full details here.
But to summarize the primary differences between the two types of Outlook data files are as follows:
Outlook Data Files (.pst) are used for POP3, IMAP, and web-based mail accounts. When you want to create archives or back up your Outlook folders and items on your computer you can use (.pst) files.
Your items can also be moved or archived to an Outlook Data File (.pst). Because a .pst file is kept on your computer, it is not subject to mailbox size limits on the mail server. By moving items to a .pst file on your computer, you can free up storage space in the mailbox on your mail server.
You had the potential to move all you emails into (.pst) file and make a full back-up of your emails.
Outlook Data Files (.ost) are used when you have an Exchange account and want to work offline or use or use the default Cached Exchange Mode. Outlook Data Files (.ost) are always copies of items that are saved on a mail server and don't have all of your emails downloaded like a Outlook Data Files (.pst), but only recent items are cached to facilitate synchronization.
When you work offline, folders that are synchronized are determined by Send/Receive groups. By using Send/Receive groups, you can choose which folders are synchronized and kept current so that when a connection to the server is not possible or you choose to work offline, you can continue to work with those items. You can also specify that updates to the Address Book be downloaded during synchronization.
You can configure Outlook to keep a local copy of your items on your computer in an Outlook data file that is named an offline Outlook Data File (.ost). This allows you to use Cached Exchange Mode or to work offline when a connection to the Exchange computer may not be possible or wanted.
With Cached Exchange Mode, you do not have to set up Send/Receive groups, choose folders that you want to be available offline, and then keep those folders synchronized.
The .ost file is synchronized with the items on the server that runs Exchange. Because your data remains on the Exchange server, you can re-create this .ost file on your new computer without having to back up the .ost file.
How to back-up all your emails from an OST file or Exchange account ?
- Open Outlook,
- Export the OST file to a PST file using the Outlook export wizard making sure that you select the
of the folder tree as the starting point along with ensuring to that "Include Subfolders" is checked. When you're done, open the PST file you just created in Outlook to ensure that everything was properly done and all the data you're expecting to be there - is there. When done checking the data, right click on the of the PST file you just added back --> select "Close".
