Microsoft 365 - Need to add .local domain to accepted domain list - Hybrid Exchange Server

[TryRestartingIt]

We have a virtual SMTP server listed as a .local address that sends document emails to Microsoft exchange users within our organization. Our registered domains in EAC end with .com.

We currently have a hybrid Microsoft Exchange environment, but as of last week, the domain's .local FQDN ended up in the Exchange non-accepted domain list.

How do I correct this and get our local SMTP server domain back on our accepted domain list?

Any help would be appreciated.

Thanks!

[#2]

@TryRestartingIt 

Hi, what version of Exchange on-prem are you running?  Must admit, I've never heard of an accepted domain randomly being removed as you describe.  Have you tried simply adding it back in?

[#3]

@PeterRising 

Our on-prem has Exchange Server 2016. 

The .local subdomain didn't have to be added in the past. It just worked. I've tried added all sorts of mail flow exceptions and whitelisting, but the M365 Admin portal in general will not allow a .local domain.

Adding the domain to our physical Exchange server didn't seem to make a difference. 

[#4]

@TryRestartingIt 

Hmm, sorry not sure then in this instance.  Have you logged a ticket with Microsoft?  I'd suggest this is the next logical step.

[#5]

@PeterRising 

I got sick of the issue, so I pointed the application's SMTP settings to our hybrid exchange server instead of the local virtual SMTP server. We are all set. I'm thinking Microsoft may be trying to add more email security obstacles.