Looking For An Open Relay SMTP? Just tested all SMTP Servers from Thailand ISP's for to get to know which could be used as Open Relay SMTP and found a total of 5 out of 29! Most of the ISP's asking for Authentication, means user will need username and password for that ISP. While searching for those Open Relay SMTP's, I came around a nice tool which checks online. On the same website are other useful tools as well and will be therefore worth taking a look at. The website I talking about is: http://www.mydnstools.info and the SMTP tool I talked about is the Open SMTP relay check under Host Tools. I was thinking that I should share the find so others could benefit from it as well.