When people join an Email group, it is great that members want to welcome these people into the group and make them feel at home. Doing this on low volume lists helps to stimulate conversation. On high volume lists though, it is suggested that these people be welcomed using their private email address rather than have several welcome messages cluttering up group related discussions. Remember that these discussions are public and meant for constructive exchanges. Treat the others on the list as you would want them to treat you.
People disagree, sometimes strongly.
Please also understand that others are also free to express their opinions. When signing up for a group it is important to save your subscription confirmation letter for reference. That way if you go on vacation you will have the subscription address for suspending mail. Attached files don't remain attached files, but instead get encoded and imbedded as part of the email. Sending out unsolicited commercial e-mail or posting inappropriate commercials is called 'Spamming'.