SMTP security application tweak ???

Hello

Newbie here so not certain if I am posting in correct area ???

I have been developing my own security application for going on 10 years written in C, we very rarely get spam as we do not store & analyse etc., I never understood why anyone would waste disk space stoing spam !!!

The system does not do any content checking our system works on the network layer in real time.

I usually add a few changes to the code around this time of year as it is reasonable quiet time & I get more time for testing. This time last year I add a 'sleep' function which seems to have got the spammers like hinet , softlayer , ovh etc. etc. very upset. They went crazy for about 6 months before they realised that they were now wasting even much more time trying to deliver their payloads - dont you feel so sorry for these monkeys !!!

Thinking we might add the ability to 'query' the incoming MX server for a response on port 25

I have been using telnet to check incoming SMTP servers from ebay , outlook , google etc. & they all respond very quickly to the query while I had the inbound connection sleep for up to 10 seconds.

Does anyone have any experience with checking inbound SMTP connections in real time ???

TIA

NG