I have an odd issue hopefully some light can be shown on. I tried searching the forum and I didn't come up with results.
I have a Barracuda 400. There is one domain trying to send mail to my clients but there is no record of communication that the domain is attempting to send an email. All was fine then one day it just stopped working. I do not appear to have trouble receiving email from other domains, but under these circumstances I can't say that with authority.
The message log doesn't list the domain nor IP as blocked, same as the syslog. I have added the domain and current IP to the whitelist to no effect. I did not make any changes to any settings to the firewall. We have been using the appliance since 2008 without incidence.
I appreciate any insight that can be provided.