I've got a classic ASP page that sends emails to registered users.
From one month to date, some users which have their emails on 3 specific domains, are not receiving emails. Some others with their emails on the same 3 specific domains receive their emails without problems.
My ISP does noticed nothing strange and says that what I'm doing to send emails is correct. This is my email sender configuration:
dim email
set email=server.CreateObject("aspSmartMail.SmartMail")
email.Server="localhost"
email.ContentType = "text/html"
...
How can I investigate to understand what is sometimes going wrong?