Mail is not being sent to a specific domain, what is wrong ?
There are may things that could be wrong. Here's where to start:
- Check to ensure that the Mx entry for the domain points to the domain.
- Check to make sure the domain resolves.
- Check the exim logs for errors or delivery of the message: /var/log/exim_mainlog and /var/log/exim_rejectlog
- Is the domain's mail being delivered to another server? If so, is the domain's MX record pointing to that server?