I'm new at my job and was advised to disable Direct Send due to some known issues. However, since I did that, users with an "onmicrosoft" email address for SMTP can no longer receive internal emails. I came across a discussion that seemed to be the opposite issue of mine and I'm wondering if anyone can help clarify what went wrong or how to resolve this?
6 Answers
You likely don’t have a mail flow connector set up for Exchange Online (EXO), and the accepted domain isn't configured in your local Exchange environment. Running the Hybrid Configuration Utility again can help fix these issues and restore your email flow.
Disabling Direct Send without adding an email connector to your domain definitely caused this issue. You have two options: either turn Direct Send back on or migrate your users to a custom domain and set up that connector. It's crucial to handle it properly in a hybrid environment.
If you’re not using an external mail filter like Hornetsec, consider just re-enabling Direct Send. It’s simpler and can resolve your problem more efficiently.
Should I just clear out all the onmicrosoft addresses altogether?
Unfortunately, you can't remove them entirely. They're tied to your Azure AD, so it's best to work around them.
Using onmicrosoft for SMTP can cause issues; it’s a common pitfall. You should explore why you're using that as your primary domain, especially in a hybrid setup. Sometimes, blanket changes like disabling Direct Send can impact your email flow without you realizing it. It might be worth checking what your actual needs are first!
Thanks for the insight! I'm just figuring things out here, so I appreciate the advice.
That's a valid point. It’s not necessarily wrong to use onmicrosoft, but you should ensure that any changes won’t disrupt your email flow.
Are you asking if the issue is that on-prem users can't send mail to Office 365? Also, check if your emails are complying with DKIM/SPF/DMARC. Those settings could impact delivery.
We actually do use Hornetsec for filtering. Might have to rethink the setup then.