On Wed, 20 Dec 2023 16:11:05 +0100 Christoph Brinkhaus <c.brinkh...@t-online.de> wrote:
> > I have heard that there is a countermeasure against spam run be big > mail providers by rejecting the first contact by SMTP and accepting > the next contact. Most spammers seem to try just once. > > I am not sure if this is 100% true For many years my SMTP server has requested an ident (TCP port 113) from outside sending servers. Since nobody now runs ident servers, there will be no reply, and my server waits for a timeout of thirty seconds before continuing. All legitimate mail servers will wait that long, spambots won't. But a failure by these mechanisms would be reasonably repeatable. My server has occasionally rejected Debian list posts for lack of DNS information, presumably when the DNS server is very busy. This is not repeatable, and is quite rare. It never happens multiple times, so my score never gets anywhere near unsubscription. I was once kicked off because my phone line died for several days. I'm not sure a temporary server failure is a good reason for unsubscribing someone. -- Joe
