When sending an outgoing mail via SMTP, in the HELO/EHLO message, Mozilla should send the FQDN for the host from which it is sending the mail, using reverse DNS lookup (if necessary) to determine that name. IOW, mozilla should honor RFC 2821. According to RFC 2821, section 4.1.1.1, when sending the EHLO or HELO message, the sender is supposed to include the FQDN of the sender's system. The RFC allows the sender to send an "address literal" (a hex representation of the sender's IP address) when reverse DNS isn't available. Many SMTP servers do reverse DNS lookups on the peer's IP address, and reject the connection or indicate some other problem in the Received line when the EHLO/HELO name doesn't match the reverse DNS name. Mozilla 1.3.1 does not send the FQDN of the sender's system. Instead, it extracts the domain name from the sender's From: address and sends that. AFAIK, that is NEVER the right thing to do. With one of my mail service providers this causes Received headers like the following: Received: from FROM-DOMAIN (REVERSE-DNS-NAME[IP-ADDRESS](untrusted sender)) where FROM-DOMAIN is the name mozilla supplied in the HELO/EHLO message, REVERSE-DNS-NAME is what the server got when it looked up my IP address, and IP-ADDRESS is my IP address. This "untrusted sender" message causes many SMTP servers to bounce or drop the message, presumably as an anti-SPAM measure.

*** This bug has been marked as a duplicate of 68877 ***

verified.