Mailbox migration to o365

I have 2 users with mailbox size over 100GB. I have migrated over 400 smaller mailboxes to o365 (Exchange in hybrid environment) and planning to tackle this next.  What is the best way to migrate these users?
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timgreen7077Exchange EngineerCommented:
shrink the mailbox sizes. you need to export some of that mail to a pst or move it to another mailbox like an archive or something. I know there was a 50GB mailbox limit in o365 but I think it just increased to 100GB, but it depends on your license. shrink the mailbox size before the move.
it depends on what license you have
if it's E3, it's having unlimited quota with 1st cap on 100gb
you need to request Microsoft to increase quota beyond 100 gb
if it's E1 then limit is 50 gb and if archival is taken, 50gb for E1 and unlimited for e3 with 1st cap on 100 gb
once u came near to 100 gb, need to check with Microsoft
delete unwanted mails if possible
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NegashAuthor Commented:
It is an E5 license. I can shrink the mailbox by exporting oldest emails to a PST file to reduce size of a user’s active inbox to less than 100 GB. And then migrate the active mailbox  which is now less than 100 GB  to Exchange Online. My question is, how do I import PST file into the Exchange Online Archive mailbox?

As another option (may be the better option), I tried to Archive older emails in Outlook (before migration) but the Archive folder briefly appears in the folder view and disappears
timgreen7077Exchange EngineerCommented:
To import into an Exchange online archive see the below link. This is what we have to do in order to import into an online archive. You can also just drop and drop from the pst into the archive but that method can be a bit lengthy and causes outlook to stop responding at times while moving the mail. these are the 2 ways you will have to do it. Either via the link below which works great and alot quicker, or via outlook dragging and dropping from the pst.
NegashAuthor Commented:
I was able to get these users delete old emails and shrank their mailboxes to a manageable size (~80 GB) so I can migrated them to o365

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NegashAuthor Commented:
Exporting old emails to a PST file and importing it as an Archive to o365 seems to be a convoluted process. So I convinced the users to delete old emails and empty items from their deleted items folder and shrink their mailbox to an acceptable size for me to migrate them to the cloud.
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