We have a client who just had his computer wiped clean and everything reinstalled. Everything was working fine, until today. He has ACT 2008 installed using Outlook 2003 as its email client. If he originates a message in Outlook, it sends without issue. If he replies to a message, or originates a message via ACT, then the messages get sent, but they stay in the Outlook Outbox.
I have been able to replicate this 100%. Messages started from scratch work fine. Replies to messages I email in to him are a problem.
I am currently checking for Office/Microsoft/Windows updates, but ACT 2008 is up-to-date. The reason I mention ACT in a couple of spots is that it has installed its software agents inside Outlook to allow him to attach contacts and email to the ACT contacts.
Any ideas where else to troubleshoot?