Hi solonstampoulis,
Good day. Thank you for posting in our forum.
To isolate whether this is a client side or an account side
issue, please check whether you can reply or forward a mail on the Outlook Web App.
Meanwhile, let create a new Outlook profile, add
the email accounts, then perform reply or forward and check if it works as
expected.
You may refer to the following article for instructions on how to a create new
profile. Meanwhile, please check the updates of Outlook.
http://office.microsoft.com/en-us/outlook-help/create-an-outlook-profile-HA102749460.aspx?CTT=1
If the issue persists, could you please provide us the error
message and the email in the private message
? In addition, may l know if all the messages you try to reply have this issue? We are happy to do more research for
you. Thank you so much.
Best regards,
Nerissa