In a previous tip, you mentioned that it is not recommended to store pst-files within Cloud based storage folders like OneDrive or DropBox.
I still have lots of space left in my OneDrive and DropBox accounts but not a lot of space left in my mailbox.
Is there really no way I can use all this space to archive my emails to the Cloud?
As mentioned in the previous tip, due to the size of and the file lock on a pst-file when Outlook is running, synchronizing a pst-file with cloud based storage will result in pretty much a never-ending synchronization cycle and could result in data corruption and even data loss.
Best thing to keep in mind; OneDrive is the cloud solution for files, not emails.
Archiving individual messages to OneDrive or DropBox
When you only want to archive a few emails to OneDrive or Dropbox, you can do so by simply dragging the messages out of Outlook and into the OneDrive or DropBox folder on your computer. You can then remove them from Outlook to free up space.
As these messages will be stored as individual msg-files, there is no problem with synchronization whatsoever.
However, since these messages are now located outside of Outlook, searching through them or sorting them as flexible as you could in Outlook is no longer possible.
You can drag and drop messages out of Outlook and into your OneDrive folder.
Archiving mail to Outlook.com or another online mail archive
When you talk about Cloud storage for emails, you are actually talking about a mail server. This is the most efficient location to store your emails in and make sure it is available to you everywhere.
If you have a large enough mailbox, you can connect to it via IMAP so that all your emails remain online and Outlook syncs all mail folders with the mail server so they are also available offline. When you currently connect to your mailbox via POP3, you can switch to an IMAP account as described in: Convert from an IMAP account to POP3.
If you only have a small mailbox or a POP3 account, you could use another mailbox server such as Outlook.com for archiving instead. Outlook.com is a free mail service from Microsoft and offers basically an unlimited amount of storage space. You don’t actually have to use it for emailing, you can just use the space for archiving.
For instructions to configure your Outlook.com mailbox in Outlook, see: Adding an Outlook.com account to Outlook.
Once you have the Outlook.com account configured in Outlook, you can simply drag and drop your messages from the folders of your current mailbox into a folder in the mailbox of Outlook.com to archive it to the Cloud.
Note 1: As an alternative, you can also completely switch over to Outlook.com. Within Outlook.com, you can configure your current email address as a connected account and collect emails from it. When you have or want to use your own mail domain, then you can sign up for Outlook.com Premium.
Note 2: Instead of using an Outlook.com account, you can also use a Gmail account or switch to Exchange Online (part of Office 365 for Business) which offers 100GB of storage and supports more Outlook features than an IMAP.