Hello, 

I have issue when sending email to some addresses. Server respond with:

Remote Server returned '550 5.1.0 RESOLVER.ADR.InvalidInSmtp; encapsulated INVALID address inside an SMTP address (IMCEAINVALID-)'

My enviroment: Exchange 2013, Outlook 2010 - no cached mode. Issue happend with two email addresses but not always.

Any suggestion, how to resolve issue?

Thx.

Clear the Outlook name cache entry for this address. If you have a stored contact for that address, remove it, and check if it's also present in the GAL. If present - remove it from the GAL/recreate it. If replying to older emails, clear the "To" address and type it in manually or select the newly created entry from the GAL.

Hi Tomas,

Does this issue occur in OWA? How is the impact, only one user or all users?

Please try to run Outlook under safe mode to avoid add-ins and AVs.

If there is any 3rd party add-ins, please try to disable them for testing.

Thanks