test this. send yourself an email using KSC internet. check the full headers of the email
if you find a line that reads
X-IronPort-Anti-Spam-Filtered: true
it means that YOUR OUTGOING email IS being scanned and you are at RISK of loosing emails that score as spam. or even worse your subject will be modified to
Yes, most ISPs are blocking SMTP ports commonly used to send mail, and force users to send mail through their own service.
ISP should keep their tracking and scoring results to the headers of the emails. when ISP take the liberty of adding wording to the subject or body of the email, its like the postman will add words to your postcards.
like adding "I love you too" to your love postcards.... does not make sense.
KSC does that. The head engineer i managed to speak with told me that i am misusing their service by...sending an invoice through an "home use" account ? I could not believe it !!
So darn KSC and 3BB and True as well. Only ISP sell you services and deliver only fraction of it without getting sued.
Lucky me, I own my server, so i can set up SMPT on any bloody port I wish.
widely available ! any supermarket or spice stand or curry paste stands at fresh markets carry it. ask for กระวาน [grawaan]the thai cardamon is called in English black cardamon