I received an email from a German CB operator named Dieter (I presume he is a CB operator from the callsign) asking if I knew of a program to design a SuperMoxon antenna for 27 or 28MHz. I replied, as I would have done to a licensed amateur who had asked the same question, that I didn't. The SuperMoxon was designed and made by Ron, GW3YDX. Only he knows how he designed it.
My reply to Dieter's gmx.de email address bounced back with the message: "Sorry, your envelope sender has been denied: The recipient 550 5.1.1 does not want to receive mail from your address."
Dieter wouldn't have known, since he contacted me through the form on my website, that I use a Gmail email address. So if I understand correctly, the German ISP gmx.de is blocking all mail from the largest email service in the world (though I suppose it's possible that it is only blocking email from me.)
I guess this has something to do with preventing spam, since I read recently that a lot of spam comes from fake Gmail addresses. But if gmx.de can't distinguish spam from real email - something Gmail does extremely well, and one reason why I've been very happy to use this free email service - then perhaps it should stop using half measures and turn off email altogether rather than leave its customers wondering why they don't receive replies from some of the people they contact?