iRule to modify SMTP mail content

Hi All, Thanks for all the help. I tried the above code and i still get the same issue. The am not able to post the logs here as they are too huge. The switch condition never gets triggered. The moment the DATA starts, i see a RSET in the logs and the mail hangs. I was able to collect the TCP DUMP in F5 with and wo the iRule and i see the below:

Without iRule: C: DATA smtp > 50509 [ACK] Seq=168 Ack=165 Win=4358 Len=0 S: 354 Start mail input; end with . C: DATA fragment, 1398 bytes smtp > 50509 [ACK] Seq=214 Ack=1563 Win=5756 Len=0 .. and the data stream follows

With iRule: C: DATA smtp > 50509 [ACK] Seq=173 Ack=165 Win=4358 Len=0 C: DATA fragment, 6 bytes smtp > 50509 [ACK] Seq=173 Ack=171 Win=5364 Len=0 .. and nothing happens after that

Here it is very clear that with the irule, the F5 never responds with "354 Start mail input; end with .". I guess, the Exchange server is expecting the remote server to respond before sending the data packets and since that does not happen here, we are seeing the hang. Any idea. Thanks, Ajay