See "Symantec Support Document ID: 2001012217141054" and "Symantec Support Document ID: 2005112111343354" for information about this event.
I searched high and low for information to resolve this issue. Symantec responded with "this is normal" as did many tech sites. However, I found these Symantec documents that were very helpful in resolving the issue: Symantec Support Document ID: 2001041813333254, and Symantec Support Document ID: 2002121812110654. The error seems to have stopped immediately and with no noticeable repercussions. It is important to note that once you look in the Detail Report to identify what is causing the termination, you may see "Message headers contain nonstandard SMTP line terminators". Once you apply the changes you may still get the initial error except it will be because the message contained NULL characters not <CR> or <LF>. This is by design. Refer to Symantec Support Document ID: 2003041109384654 for more information on this secondary issue that may appear in the event log as well. This process will greatly reduce the amount of errors and warnings.
See "Symantec Support Document ID: 2005120511355054" if you are using Symantec Mail Security 4.1.x for SMTP.