SPAM, Email Blocking and

I'm not getting email from my mailing list anymore, and I can't get a response from

If you can't receive mail from, or aren't receiving all messgase from a list, it could be that something or someone is filtering your mail, and rejecting mail from us as spam.

Most likely you can't get our mail because of a spam filter that your ISP has put in place on their mail servers, or filters that you've installed on your own computer. Either of these might block mail from as 'collateral damage'.

Spam has become an increasingly large problem for all of us. So much so, that many ISPs and desktop spam-blocking software packages have started using aggressive methods to try to stop it. Unfortunately, some of those methods also block a lot of real mail, even messages that you've specifically asked to receive.

If you're using a spam blocking method called Challenge-Response, (this appears under many names, including SpamArrest, Mailblocks, Matador, TMDA, and more) which requires correspondents to reply to an email or go to a web site to 'verify' themselves before they can send mail to you, please read Why Challenge-Response is a Bad Idea. policy: If you send a challenge to any of my personal addresses, it will be treated as spam and discarded unread. If you send challenges to the majordomo address, to a list or listowner address, or to contributors of a mailing list that you subscribed to, there is a strong possibility that you will be banned from subscribing to that mailing list, or be prevented from sending mail to at all. You may never know what happened, because I won't be able to send you an explanation (read the first sentence of this policy again.) It's entirely your own responsibility to figure it out and deal with it. I currently entirely block mail from the following domains from, which do nothing but provide challenge-response services:,,,

Before you call your ISP

First, be sure that you aren't blocking us yourself.

If you're using filters (sometimes called 'rules') in your mail client (Eudora, Outlook, etc), or a desktop filtering package such as SpamAsassin, turn them off for a while and see if that lets all of mail get to you. If so, you'll need to adjust your filters. As a general rule, you should transfer mailing list messages to their own mailboxes BEFORE applying any anti-spam filters. Don't use a subject line tag for this! Use the Sender or List- header lines. Set any spam filters to move suspected spam into a special mailbox instead of deleting it unseen. That way you can scan the spam mailbox to make sure that your filters are working the way you expect.

If you aren't getting any message from, you can always tell to send you a message for testing by sending a message to with a command of 'help' in the body. If you don't get a reply within a few minutes, a spam filter at your ISP might be blocking it.

What you need to ask and tell your ISP

If you're certain that your own computer isn't throwing away our mail, ask your ISP what spam filtering methods they're using, and ask them to determine if those methods are excluding all mail from, or if they might be discriminating against mailing lists--perhaps by filtering on the word 'bulk' in the headers, or because the list sends to multiple addresses on the server at the same time. They might also be throwing away particular messages that the filter thinks is spam bacause someone legitimately used a word or phrase that spammers often use (such as 'for free').

Tell them that you want to receive mail from They should be able to 'whitelist' to bypass their regular filters. Good ISPs will be happy to help rather than lose you as a customer. But you must talk to them yourself--I don't pay your ISP money, so they have no reason to listen to me. They do have a reason to listen to you. If they tell you that whitelisting is impossible, or if they want to charge extra because it's 'difficult', consider finding a new ISP. Whitelisting is a standard industry practice, and you are, after all, paying them a monthly fee to know how to run a mail server, and to get your mail to you. It shouldn't take them more than a few minutes to take care of it. If they say that they need more information from me, I'll be happy to talk with them. Have them send mail to postmaster at

A little more background

There's a continuum between stopping every possible piece of spam (easy: block all mail) and making sure that you receive every bit of good mail (easy: don't do any spam blocking at all). Most ISPs and individuals do something in between. They choose one or more methods that block a lot of the spam, while letting through most of the real mail. Unfortunately, there isn't yet a way to discriminate perfectly. The more aggressive you are about stopping spam, the more real mail you'll lose as a side effect. Spam filtering techniques vary from looking for key words and phrases in the content of each message, through blacklists that block mail from specific domains that have been proven to send spam, up to blocking off entire ISPs and webhosting companies, which can also block mail from many hundreds of innocent companies using those ISPs or webhosts. It's this last technique that's the most likely to block mail from domains that do not, and never have, sent spam.

It's quite likely that you are letting someone else make this decision for you. Most ISPs either block spam automatically for everyone (often using several different methods) or offer you the option, either for free or for an added price, to use such blocking. What they don't always tell you is that they may be blocking some genuine mail too--maybe a lot of it.

If you use anti-spam software on your own computer with the default settings, you are also letting someone else decide for you. Read the manual and learn how to adjust the filtering to suit you and the kind of mail you want to receive. I'm sorry, but I can't help you with this. There are too many programs out there and I don't use any of them.

If possible, you should use an anti-spam method that lets you examine which messages are discarded. Use a method that lets you adjust the filtering to match your needs, not the needs of some mythical average user. Most desktop software lets you adjust how the filters work. You'll need to read the instructions and do some experimenting. If your only filtering is through your ISP, ask them to help you adjust the settings for your account.

For more information about spam and spam filtering

Does use any spam blocking services?

Yes. In addition to rejecting incoming mail from servers that don't have a valid domain name, rejects mail that is listed in the following block lists. These lists are very conservative and should not affect genuine mail. If you do get a rejection when trying to send mail to, contact your ISP and have them fix the problem. If they need to contact me, have them send mail to postmaster at tardigrade.ORG.

All mailing lists on require confirmed subscriptions, usually by means of a ' confirmation key'. When you ask to be subscribed to a list, majordomo sends a message to the subscription address to confirm that the owner of that address really wants to be added to the list. You must reply with that key before actually being subscribed. Only subscribers are permitted to post to a list, so even if a spammer tries to spam the list address and it gets past the server blocklists, it will bounce to the listowner as a non-member submission.

Send mail to the Webmaster:     Monday, 03-Jul-2006 18:57:46 PDT.