Email blocking

Discussion of features in Mozilla Thunderbird
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Joined: March 29th, 2015, 11:27 pm

Post Posted March 29th, 2015, 11:37 pm

I would like to see as a feature in Thunderbird the possibility of automatically bouncing unwanted emails from a specific person. I have a filter to send such emails to Trash, but this is not sufficient for my purposes. What I want is an un-welcome mat.


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Joined: July 30th, 2003, 5:06 pm

Post Posted March 30th, 2015, 1:39 am

By the time a email client sees a message it is too late to truly bounce it, despite what fans of Mailwasher etc. believe. It is not enough to mimic what your SMTP server would send if it bounces a message, it needs to be done over the TCP-IP connection that the sender made to the recipients SMTP server. The email client has no way to even see that connection, so its trivial for somebody to detect and reject any bounces sent by a email client. Attempts by email clients to bounce a message also create a lot of spam as frequently the sender spoofs the From: address.

Given how ridiculously cheap it is to send spam, it wouldn't do any good anyways. For example, one of the techniques spammers use to find valid/existing email addresses (a directory harvest attack) is to use brute force guessing of valid e-mail addresses at a domain using different permutations of common usernames.

I suggest you read the section about using SpamPal with the junk mail controls in

If you're not trying to deal with a spammer, and just want to bounce messages from a specific person see what your email providers webmail user interface (browser based) supports. Some support both message filtering and also letting you specify a few addresses that they will (truly) bounce. If they support the latter, that will work since its integrated with the SMTP server. That works regardless of whether you read your mail using webmail or a email client.

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