Have a site on ISPConfig using dns and mail servers from 1and1 The site is and e-commerce (oscommerce) website and needs to have email requests for info forwarded from the site to a 1and1 mailbox (pop3), which has been set up and works. I can send a manual email from the site to anywhere and get it delivered INCLUDING the 1and1 address. I can generate and email request via a form and php script from the site to any address I specify and get it delivered EXCEPT to the address at 1and1. I can deliver from the site to my gmail address and have it forwarded by filter to 1and1 and get it delivered. If I use the 1and1 address as a forwarding target from an email address at another (unrelated) site on the same ISPConfig server, call it address A, then send an email it DOES NOT arrive at the 1and 1 address call it account B. If I send the same email from this address (A) to my gmail account with an automatic forwarding (filter) to B at 1and1 it arrives. Why can I not forward direct from account A in IspConfig to account B at 1and1?