Messaging Gateway

We are experiencing what is becoming a reoccurring issue with our SMG 10.1-2 where randomly we will experience a message slow down on inbound messages.  We do not see a build up of messages in any (inbound, delivery or outbound) queues. We do notice that a telnet session will start to become very slow updating and making initial connection.  Outbound message delivery is normal.  This will become worse and outbound message delivery will(may) become effected.  After some time this appears to go back to normal operation (without intervention) and messages start flowing again.  If we restart the MTA this seems to immediately correct the slowness and messages & connections return to normal.  I have not been able to with any certainty say this is caused by excessive connection attempts using the firewall connection stats -we only have real time no logging.

Has anyone experienced similar issues -that can be associated with SMG, and do you have recommendations as to where I can look to see if the root cause is something wrong with SMG or maybe the SMG is just performing the way it should throttling in response to outside influence.  As stated I do not have any firewall logs nor do  I have access to the firewall interface to check its connection logs / or attempts at the time of the slowness.

Please check the following,

The issue may be due to one of the following reasons

1- Too many content filtering rules

2- Size limitations for incoming messages. (Sometimes adjustment helps)

3- Lesser resources allocated to SMG as compared to required (Sizing Issues)

You can try installing an additional SMG, however best way is to upgrade the SMG to 10.0.2 vesion which is efficient to handle performance issues. 

Thank you I'll look in to your suggestions;

1- we currently have many rules that had to be created this way due to the need for a different inbound and outbound rule for every office.

2-Not sure if you mean just adjust the message size limits or set them. We currently restrict email to 20MB.

3 we have this on a 4.1 VM server using 4 processors and 6GB of Memory.