You can change the count of messages allowed per session on the exchange virtual server for that server. That will afect only the server you make the change on. If the other servers are not getting this error then you do not need to make the change.
Open Exchange Systgem Manager, expand administrative groups, then your administrative group. Expand servers, then your server, then protocols, then SMTP. Right-click your SMTP virtual server, choose properties, then go to the messages tab. Change the “limit number of messages per connection to” whatever value you want it to be, or even disable it by unchecking the box. That will remove all limits for that selection.