I am still new to SolarWinds products, but all the documentation I have found specify RFC3164 for the Syslog message specification. The RFC is very specific on the format of the TIMESTAMP field, it much use ':' as delimiters within the timestamp. The hostname or IP address is fine. If you want to create TAG field for the Appname, then it will need to end with a ':' character; otherwise Appname is assumed to be part of the MESSAGE text. The RFC specifies all the minute details. Try the following and see if this helps...
<25>Jul 10 18:04:33 Hostname Appname: Message