As an Exchange Admin, everything is running well and you come into the office and you have a ton of calls logged by users who cannot send/forward or reply to emails on OWA. You think hard about any changes that have been made, and well, none have. You take a look at one of the errors and see the following:

Something went wrong and we haven’t been able to send your message yet

Not a nice thing to see. Here is the error presented to the end user:

Check if your Exchange Servers are performing proper DNS lookups/resolutions, IE, perform a ping to your domain controller from your Exchange Server, it might be a case where it has lost connection and you are getting the above error.

Hope it helps.