Emails disappearing, not coming through

We are seeing some emails that are sent from outside our system, they reach us and are processed (received and sent on), but then they never show up in the inbox. I’m not the admin, so I’m short on technical details, but here is what we see (IPs and addresses altered) after I sent a simple text email from outside:

Mon Dec 13 17:31:53 2004
MAIL RECEIVED:
Received from IP address: 64.-.-.-
Sender:
Recipient list:
MessageID: 1102987912832
Size: 1087 bytes

Mon Dec 13 17:31:53 2004
MAIL SENT:
Sender:
Recipient list:
MessageID: 1102987912832
Size: 1087 bytes