Public folder alternatives in the big 2026?
Posted by Murhawk013@reddit | sysadmin | View on Reddit | 35 comments
I’ve never used public folders before till I joined new org that relies on them heavily for calendar sharing. I think we have around 200 with only 10-15 of them being over 1GB in size.
I tried looking this up and seems like the options are Microsoft 365 groups, shared mailboxes or just sticking with PF’s. Our use case is literally just the ability to give granular permissions to a shared calendar…is this something that can be done with a M365 group? I’d really love to move away from PF’s as they’re a pain in the ass and want to modernize our processes.
sderby@reddit
M365 group/shared mailbox/SPO
GremlinNZ@reddit
Last I checked, group mailboxes have a hard limit of 50GB, so shared mailboxes etc are better, as you can licence and increase.
Wolfram_And_Hart@reddit
You are thinking .PST files and old Outlook is going away.
INSPECTOR99@reddit
"old Outlook is going away" Hhhmmm, WHen??
Wolfram_And_Hart@reddit
It was supposed to be this year but they have pushed it to 2028-29 since New Outlook was not completely baked and LOTS of 3rd party addons had not updated yet.
GremlinNZ@reddit
Nope, not PST (and they can be increased with a regedit, if you enjoy some pain), but happy to be corrected.
Last I checked (and ran into it for a client a couple of years ago) group mailboxes can't exceed 50GB.
Wolfram_And_Hart@reddit
My mistake. It’s early.
It’s limited to 50gb for “free” you can add another 50gb with the online plan 2.
GremlinNZ@reddit
I don't think it's possible to licence group mailboxes.
Shared yes, and yes, have added a P2 to Shared mailboxes before.
Wolfram_And_Hart@reddit
I guess I’ve never had a group mailbox get that large. Yeah just checked. Wild.
GremlinNZ@reddit
Haha, one of those things you want to find out before you start using it, as you can't convert a group mailbox to a shared one either!
Wolfram_And_Hart@reddit
That’s just a late night mail migration. I’ve done that plenty of times.
garbageadmin@reddit
We just went through this. M365 groups for sure. They automatically add to Outlook desktop/mobile and it was easy to copy/paste most calendar items.
Create new groups / inform users of change / set public folder rights to read-only across all / give 2 weeks before removing access to pub folders / job done.
Curious201@reddit
for public/shared folders i would first separate the problem into storage, permissions, and calendar visibility, because one tool rarely handles all three cleanly. if this is mostly shared files with some shared calendar needs, Teams or SharePoint backed by M365 groups may be the most natural replacement, but only if you are willing to clean up permissions instead of recreating the same public folder mess in a new place. public folders usually become painful because nobody owns the structure, old mailboxes sit there forever, and permissions grow by accident. i would map the top folders by actual use, decide which ones are still needed, archive the dead ones, and only migrate active shared work into Teams/SharePoint/shared mailboxes. if the main requirement is just a shared calendar, a shared mailbox or M365 group calendar may be enough without turning it into a giant migration project.
Murhawk013@reddit (OP)
Yeah it’s 99.9% just shared calendar use. The only thing with the M365 groups is I don’t believe we can have the different permission levels? We could probably get away with it if it was at least owner vs standard member that can’t delete others appointments.
Curious201@reddit
yeah, that is the awkward part with M365 group calendars. they are cleaner than public folders, but the permission model is not as granular in the same way people are used to with PFs. if the real requirement is “many people can view/add, but only a smaller group can edit/delete other people’s appointments,” i would test a shared mailbox calendar before committing to M365 groups, because shared mailboxes still give you more familiar mailbox folder permission options like reviewer/author/editor-style access. for 99.9% calendar use, i would inventory the 10–15 calendars people actually care about, build one pilot shared mailbox or group calendar, and let a few real users try the exact create/edit/delete scenarios. the worst move would be migrating 200 public folders and then discovering one permission edge case was the whole reason they kept using them.
ZAFJB@reddit
SPO
Visible_Spare2251@reddit
Aren't calendars in SPO basically deprecated?
ZAFJB@reddit
Use Outlook for Calendars.
FutbolFan-84@reddit
You can use a shared mailbox for this. The calendar is essentially a "subfolder" of the mailbox and you can set permissions on the subfolder very granular using PS.
Murhawk013@reddit (OP)
My only concern with shared mailboxes would be performance issues if a user has access to say 10+ calendars/mailboxes. Idk if that’s a valid concern but only thing I can really think of with it
ADynes@reddit
We were having ton of PST issues, we have expanded ours to allow up to 150 gb, but still had them randomly getting corrupt. What we ended up doing was turning on cache mode for the user mailbox but online mode for all shared mailboxes. This way it wasn't cashing things locally. Slightly slower but our PST files dropped in size and no longer get corrupt.
We have users with access to six or seven shared mailboxes and performance isn't bad. It's actually better an online mode even knows a slight delay when opening stuff than it was having everything locally
FutbolFan-84@reddit
I've had 30+ shared mailbox calendars in my own mailbox and did not notice any performance issues. Not had a use case where more than that was required. I'm not sure how well it would scale up if you had many dozens or even hundreds. I'd be pretty confident running up to 50.
dat510geek@reddit
I think there more talking in the sense of the old classic 50gb ost limit and shared mailboxes filling it. Maybe but there are settings you can adjust
GremlinNZ@reddit
Depends whether the mailbox is auto mapped (data goes in default OST) or manually mapped (separate OST).
Visible_Spare2251@reddit
We still have a load of public folders in use for filing project related emails for all the team to access. I have not yet looked at finding a decent alternative that will work in new outlook long term.
FastFredNL@reddit
We got rid of public folders when we moved to Exchange Online. In some cases some departments wanted a shared calendar but not a mailbox which is what we used public folders for. We use resource/equipment calendars for this now that people can just add meetings in themselfs.We got rid of public folders when we moved to Exchange Online. In some cases some departments wanted a shared calendar but not a mailbox which is what we used public folders for. We use resource/equipment calendars for this now that people can just add meetings in themselfs.
7amitsingh7@reddit
In 2026, Public Folders aren’t really needed for shared calendars. Microsoft 365 Groups have limited permissions, so they’re not ideal. Shared mailboxes are the best option since they support shared calendars with detailed permissions and are easier to manage.
Daphoid@reddit
Run away from public folders. Heck even shared mailbox calendars for users sounds silly. A group member (but m365 groups are nicer with more features). But for a manager to see my calendar beyond free/busy? That's just a powershell automation if every manager wants it.
Disorderly_Chaos@reddit
I wish I had a solution for you. Our corp still uses shared mailboxes as calendars.
Murhawk013@reddit (OP)
I feel like m365 groups would work perfect besides the granular permissions
longmountain@reddit
Can you go back to your old job? #publicFolderHate
gafftapes20@reddit
Are you just trying to give base permissions to everyone’s calendar? In azure I have a powershell script we run. You can’t give group access to a calendar, but in your script you just grab the group, extract members, and give them specified permissions to the persons calendar. We currently don’t use shared calendars though, so maybe there would be a purpose to configuring a shared inbox and having users access to a central calendar.
Murhawk013@reddit (OP)
No apparently they’re used granularly i.e. manager should have Owner and team members only ability to edit their own appointments but not others.
I wish I could just pass the responsibility on to them to be trustworthy adults lol but not my fight to pick.
Ok-Double-7982@reddit
That sounds corny.
What's the exact use case? Visibility into the employee's vacation time off? Or visibility into an employee's customer meetings or appointments?
There's a few ways to accomplish both, depending on what they're trying to do.
Murhawk013@reddit (OP)
We’re a hospital so believe it’s appointments and there’s PTO calendars as well.