O365 email local cache

Work uses O365 and I'm getting a little frustrated with OWA. Thinking about running a local email server to mirror O365. In the end, I want to keep my email in O365, but have a 2 way sync with a local imap server. Looks like I have a few options on the email server - dovecot/cyrus/stalwart. For the syncing, I just see mbsync. Any experience setting up something similar? Any other options other than what I listed?

Edit: IT knows what I'm doing. I'm not going to compromise any compliance requirements we have.

mystik ,

IMAP on O365 now requires "Modern Auth", which requires OAuth to authenticate access to mailboxes. Anything that connects via IMAP will need to be approved by the admins at this point (Including Thunderbird). Without the cooperation of your organization's IT team, you are not going to get far.

Toes ,
@Toes@ani.social avatar

If I was in your IT department I'd be required to shut this down and probably revoke your access until our bosses decide on your future.

Keep in mind, your employer has a responsibility to protect their data and this would subject your homelab to any legal liabilities such as a lawsuit search order and data privacy auditing.

Any solution you work out needs to be signed off on in writing if it's outside their expected usage.

Another important point o365 requires oauth2 authentication unless your IT department has intentionally allowed other forms of authentication or they are in a hybrid legacy environment.

When they broke EWS and office 2010 compatibility they crippled many foss solutions without an additional license and the tools that do work will report details to exchange about your homelab. So if your department is diligent it'll come to their attention.

greybeard ,

M365 is doing away with all legacy authentication, do not be surprised if IMAP is completely unusable in the next 12 months. If you simply want to keep a copy of everything, a store and forward SMTP proxy would probably be the solution, so all email going to your domain would hit that first, then send off to M365.

slazer2au ,

No, oh god no. What you are talking about can arguably be classified as Shadow IT and can get you into trouble depending on your orgs certifications.

If you have O365 that should entitle you to Outlook and use that instead or ask your org IT what alternatives they permit.

catloaf ,

Why? And also, have you talked with your company's IT about this? I doubt they'll enable connectivity with EWS or whatever just for you.

Your best option is to just use Outlook in cached mode. Or Thunderbird if you want Linux, assuming it supports Exchange cached mode.

tastysnacks OP ,

Yup, its already setup. I've currently got mutt running with a davmail middle, but its slow. A long time ago, we just had IMAP enabled and I used mbsync for a while with a local mbox. But it slowly turned into a mess. Since then we've enabled 2FA on O365 and so far I've only gotten davmail to work.

catloaf ,

Yeah there's not going to be any good option for you here except Outlook.

What exactly are your frustrations?

tastysnacks OP ,

I've always used multiple email clients. Mutt or mu4e for organization and tasking. OWA for quick emails and the calendar. Since we've gone to 2FA, that all stopped until I found davmail. OWA search is really bad, compared to mu or not much anyway.

I want a central server. I don't want to do mbox again.

redfox ,
@redfox@infosec.pub avatar

Have you confirmed you're not breaking corporate user policy?

Everyone has mentioned Outlook.

Also, 2FA is standard now, like eating ass.

https://infosec.pub/pictrs/image/ca838258-4bdd-4e92-802a-4fec99fa60ca.jpeg

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