Exchange 2003 To Office 365 Migration Issue

I have a client on Exchange 2003 SP2 that I'm migrating to Office 365.  I've done many of these in the past including some from Exch2003.  I'm unable to get communication to work.  I use to run an Outlook Connectivity test and got a 443 blocked error (The specified port is either blocked, not listening, or not producing the expected response.).  I've run through the RPC/HHTP config again, made sure the 6001-6002 and 6004 ports are open, I installed a third party SSL cert (client previously only used Exchange for internal email).  I can browse to https://<FQDN>/oma and https://<FQDN>/Exchange for OWA access.  I can telnet fine to port 443 from remote hosts.  Can anyone give me an idea to look at next?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Marshal HubsEmail ConsultantCommented:
Sometimes these connectivity issues could be really hard to troubleshoot, same has happened to me once. In my case, Outlook was unable to connect to the server & "offline" status was getting displayed.
To resolve the issue,

1. From Outlook’s "File" menu option, verify if there is a check mark beside "Offline".
2. If yes, click "Offline" in the File menu and allow the client to connect again.

After all manual set up, I preferred professional migration solution, rather than going for complex manual Import-Export process. I tried Stellar EDB to PST converter & successfully migrated all of my mailboxes from Exchange 2003 to Office 365 in quick time with completely intact mailbox structure.

You can know about this software by visiting:
SafetyNet-TCAuthor Commented:
This isn't an Outlook issue.  I'm using  O365 has a cutover migration process, there's no reason to use a third party solution.  Any other ideas?
SafetyNet-TCAuthor Commented:
Self resolved.  Stale DC in AD, removed with ntdsutil, issue resolved.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
SafetyNet-TCAuthor Commented:
Self resolved.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.