Apparently, the mail server used to test out certification for an ipv6 enabled e-mail address doesn't follow RFC standards when sending mail, and gets rejected by my server:
2009-07-27 01:55:50 SMTP protocol synchronization error (next input sent too soon: pipelining was
advertised): rejected "DATA" H=ipv6.he.net [2001:470:0:64::2] next input="To: \r\nFrom: email@example.com\r
\nMessage-ID: <firstname.lastname@example.org>\r\nSubject: IPv6 Certification Mail Test\r
\n\r\nPlease insert the following code"
Basically, our mail server located at 2001:470:e867::2 uses a simple way of breaking alot spambots - it inserts a 2 second delay before showing the first '220-' line. This won't break RFC compliant mail servers, but will break mail servers (mostly spam bots) that dump out the entire conversation without bothering to check to see if its okay to do so yet.
Unfortunately, it seems to affect the HE ipv6 testing mail server as well. Any way this could get fixed?