I have configured a mail server with Sendmail on my office and mails are sent fine.
I'm using MailMan to send a newsletter to a test list of five people, one from hotmail, one from gmail, one from yahoo and two from my ISP (including my address).
The newsletter is sent fine to all of the recipients (I've checked sendmail queue) but for some reason my ISP is discarding the message for their addresses (hotmail, gmail and yahoo are working fine).
I suspect the problem is related to the headers sent by MailMan because when I send the newsletter directly from my mail client trough my office server, it is received without problems (the only difference between the one sent by MailMan and the one sent by my mail client is the headers).
Is there some special header sent by MailMan that is well known as some kind of SPAM header?
Thanks in advance!