Sorry to spam the list for this, but I was not able to find anything close to a technical support email contact on their web page... To avoid many round trip mails, here's the problem: we get incoming mails with senders like <+4176...(a)mms.sunrise.ch>ch>. But: mms.sunrise.ch. 3600 IN MX 10 mm3.sunrise.ch. Host mm3.sunrise.ch not found: 3(NXDOMAIN) So, those sender addresses are invalid, and get rejected on our mail servers. Might want to fix your DNS.. Cheers, Markus