Mailbox and forward on office 365

[stewamax]

Three things worth checking:

- can an email from one email address (say fred@parentco.com) in the parent co mail domain be forwarded successfully to a different email address (say joe@parentco.com) in the same parent co mail domain

- if you change the shared mailbox to forward direct to the parent co email account (i.e. not to the distribution list), will an email from the parent co email account get forwarded back to the parent co email account?

- is there any possibility that the email from the parent co account is actually being forwarded correctly to the parent co account, but the parent co email system (what system is it?) is black-holing it because it the sender and recipient addresses are the same? (Normally this is valid, but you never know...)

[AleisterCrowley]

I will have a go when i'm out of the latest pointless whinge-fest (sorry, progress meeting)
ParentCo email is MS Outlook 2013
Your help greatly appreciated

[stewamax]

ParentCo email is MS Outlook 2013

Tnx - but what please is the email system it links to? Another O365 tenant, gmail, outlook.com,...?

[AleisterCrowley]

It's a massive corporate system, but I know our Outlook migrated to Office 365 last year (I ended up with 50 times more storage...)
I'm not up to speed how all these bits are connected to be honest

[AleisterCrowley]

Ach, got me beat
It works fine from my personal gmail account.
It's just not happening when I email the mailboxes on 365 from my work account
Spent hours trawling online help sites

[AleisterCrowley]

Well, even the 'easy' way doesn't work
I've set up a new user called something like SPinvoices
Logged in as above and set forwarding rules to me@parentco and me@365

Mail to 'user' SPinvoices from me@parentco results in forward to 365 only

Mail to 'user' SPinvoices from me@gmail results in forward to 365 and me@parentco

[Infrasonic]

Can you not liaise with a systems admin to see if there is some network, router, server or a n other setting blocking what you are trying to achieve?

[stewamax]

Does mail to 'user' SPinvoices from someonelse@parentco results in forward to 365 only or does me@parentco also receive it ?
I'm just trying to nail down whether your parent co's O365 service has some form of routing loop prevention set.

It may be worth adding the parentco domain to your O365 tenant's Admin Center / Exchange / Mail flow / Remote domains and ticking 'Allow automatic forwarding' (although that should be the default...).

[AleisterCrowley]

I suspect it is my 'parentco' email system blocking the 'loop back'
It works fine from other emails , having tried my gmail, my tenant 365 account, and I also got a bloke in our 'partnerco' to try from his corporate account

It's stuff from me@parentco failing

Seems to apply to all emails in to the maiIboxes originating from the @parentco domain, as my colleague tried from hisname@parentco and the loop back to me@parentco failed

Oddly though, if I replace the DL in a mailbox with me@parentco it DOES work- but limited to one address that way!!
Must be something to do with the characteristics of the parentco email after passing through mailbox AND distribution list

[AleisterCrowley]

..365 mailtrace is showing messages as delivered

[Infrasonic]

Loop back prevention at the top level (big co) makes sense as a way of limiting forwarding feedback loops (from potential DoS attacks or just people not paying attention to their forwarders...)

What happens if you set the forwarder address to another big co address other than the sent from one?
If that works then you know that there is a loopback prevention rule in place.
The way round that would be to have a secondary big co address that you use exclusively for your DL forwarding alerts.

[dspp]

Is there anything in your email system that prevents infinite looping ? My suspicion is that you are finding something to do with that, perhaps doing something else as well.

regards, dspp

[AleisterCrowley]

Looking at message trace on 365 it shows SENDER as me@parentco, colleague@parentco etc rather than invoices@365 domain.
The ones 'from' @parentco are showing DELIVERED but not arriving in parentco mailbox, all others OK
Is our parentco email rejecting them as they are incoming external emails apparently 'from' the parentco domain?
Can I set up so the sender is showing as invoices@365 domain rather than original sender?

All you inputs greatly appreciated of course

Yours Confusedly
AC

[Infrasonic]

You need to speak to (or email...) whoever is in charge of the admin for the email system at the main company if it's their email infrastructure that is being used by all the subsidiary companies and your O365 client.

There are so many variables (many of which may be intentionally locked down for security).
You need to find out from them exactly what you can and can't do at your local client (O365) level without their intervention. (Not much beyond the very basics would be my guess.)

[stewamax]

Parent co's O365 Exchange Server mail transport rules can be set to block almost anything, but straightforward blocking of 'external' emails from its own domain seems a bit draconian.

One other possibility is that it insists on any such emails having valid spf data attached. spf is a default when domains are added to an O365 tenant, but the spf information that accompanies an email can be stripped off when mail is forwarded. The receiving mail server may then sideline the email as spam. This stripping doesn't happen with DKIM - which is an O365 option. In other words it is possible that parent co's mail server doesn't like receiving forwarded mail using its own domain name if the correct spf data is not present.