Retaining messages beyond retention period

[PS_Exchange_Adm]

Any suggestions on how to store messages that fall outside the retention period stated in the retention policy?  I know that sounds counterintuitive (retention periods exist for a reason) so let me provide some background.

Now that are mailboxes are migrated to Office 365 I would like to institute a retention policy of 1 year for items in the mailbox solely for the purpose of managing the mailbox size.  For most users this retention policy is sufficient - they rarely need messages beyond a year's time and for those with this policy already in place it is helping to keep their mailbox more than 10 GB under the applied license's limit.  The problem is certain people need or want to retain messages for a longer period.  I'm aware I can use multiple retention policies with different retention schedules but I'm attempting to avoid that if possible.  So the question is what options do I have to maintain messages beyond the retention policy?  So far I've come up with the following ides but each have their drawbacks that I'd prefer to avoid.  Hoping someone else has another idea or two.

1) Store messages in a .PST file

2) Store messages in a separate mailbox/public folder not subject to the retention policy

3) Store messages in Teams/SharePoint

4) Store messages in folders/file share

Thanks in advance!

Chris

[#2]

Which location are you using the retention policies from? If you're using the Exchange MRM retention policies, the default MRM retention policy includes a tag of never delete. The user just right clicks the message and assigns that tag to the message. This message stays in the mailbox though. There's no native option to delete a message but keep it somewhere else (unless you use an archive mailbox). I would recommend that if the message is required to be kept, you keep it in the mailbox, rather than export it. You will lose track of items if you start exporting messages and storing them elsewhere

[#3]

Thanks Dan and I agree I would want to keep it in the mailbox. This is an interesting approach and one I will consider. Unfortunately we are going down the M365 data lifecycle policies but if this is the only approach to get the result I'm looking for I'm willing to move to the Exchange MRM policies. Thanks for the suggestion!