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48

Be sure that your emails don’t look like typical spam emails: don’t insert only a large image; check that the character-set is set correctly; don’t insert “IP-address only” links. Write your communication as you would write a normal email. Make it really easy to unsubscribe or opt-out. Otherwise, your users will unsubscribe by pressing the “spam” button, and ...


8

Unfortunately there are many different filtering techniques and some major mail providers won't publish what they use and/or what weights are given to various tests/filters, so knowing how to get through is difficult. Basically spam has driven ISPs and users into a situation where they sometimes make it difficult for such legitimate messages (especially bulk ...


8

Mailchimp have an excellent article on How To Avoid Spam Filters Update: Ok, seeing as I got slammed for just giving this link (to be fair its contents probably wouldn't solve your problem here), I've added more specific to what you're sending. I suspect its the text you're using. 'Please confirm your email address by clicking the link' - I think you ...


7

I can vouch for #2 (reverse PTR) being important, but not #4 (mail server domain matching "from"). We set up mail servers all the time, and most mail hosts don't really even care about #2. The main thorn is always AOL, and they list standards you can check off.


7

With a service, the spam e-mail never hits your network. For a large organization paying for network bandwidth based on usage, this can represent a non-trivial cost savings. A large ISP I used to work for used Postini, and when we turned it on we saw an 83% reduction in incoming port 25 traffic from the Internet. At the time (I don't recall precisely how ...


7

The main difference is that Milter happens pre-queue, i.e. before Postfix accepts the mail. Content filtering happens post-queue. It depends on the circumstances and the resources you have available. In general, post-queue content filtering in my experience is less resource intensive. Postfix handles the SMTP transactions, queue's the mail and this can ...


5

Like others said, you want to avoid "looking" like a spam message when sending the email but you can't necessarily tell what will or won't make you look like spam because techniques vary. One thing you might want to consider is sending a plain text email to your customers for each newsletter that actually contains a quick description/greeting followed by a ...


5

Aside from your HELO string and the DNS PTR records as mentioned, the bulk of the things that will help are going to be content related, not sending-sever related. Don't send out HTML email if you can at all avoid it. Don't include suspect phrases ("click to unsubscribe","privacy is important" and the like) Don't use "reply-to" headers, send from the ...


5

I've gotta agree with John Gardeniers here. Mailcleaner is by far the best opensource spam filtering solution I've found, and I've tested pretty much any that I've been able to locate (mostly those integrated into other firewall-type-linux-distributions). I've used Mailcleaner for several years now to protect my domain (stormnine.net), while using ...


5

As silverfire indicates, it depends on two things: How many emails are we talking in terms of numbers (10,000 or 100 a day?) How much bandwidth you have connected to your mail server The only thing you can do to reduce your bandwidth is to use an external spam filter, such as Postini (which is a Google service, who we have had success with for some of ...


5

I don't know Exchange, but I am quite sure that you can somewhere configure to trust every mail coming from your own servers. On a more general note some hints to avoid being classified as spam: Don't send spam (send only requested mails, make it really easy to unsubscribe for newsletters etc., don't give anyone a reason to tag your mails as spam) Try ...


5

You order of rules is very bad. If you want to keep all of them and not add anything else, the order must be: smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_pipelining, reject_invalid_hostname, reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unauth_destination, reject_unknown_recipient_domain, ...


5

From RFC 5321, Section 5.1: When a domain name associated with an MX RR is looked up and the associated data field obtained, the data field of that response MUST contain a domain name. That domain name, when queried, MUST return at least one address record (e.g., A or AAAA RR) that gives the IP address of the SMTP server to which the message ...


5

Your server is one of the following: hacked cracked Open Relay Gateway for a Spam bot A Windows server containing a Spam bot You have to hire a professional to help you out. If you want to do something on your own then you do: Network traffic monitoring Identifying mail sending process Watch mail server logs Then remove the root cause. But you have ...


5

Your email looks spammy to me. Even if I had registered, I likely wouldn't open your link. You need a lot more detail in your message. What do I do if I didn't register? Who am I confirming my address with and why? How do I contact you for more details? What is your web site? I didn't decode your base64 encoded data (why encode your html), but ...


5

With the limited information you provided, NO. But you have individual user preferences and possibly individual Bayes databases that are different? You do know that SpamAssassin adds headers with the rules that were triggered and the resulting spam score e.g. compare a regular message: X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on ... ...


5

Is there a way to force UCEProtect to change their policies? No. They're going to use whatever policy they feel works best for them. You mention standards and guidelines. There IS RFC 6471 , but do keep in mind that is considered "informational." Even if it were a standards-track RFC, its not like you can force UCEProtect to comply with it. That said, if ...


4

Different mail servers and different organizations use a variety of different ways to combat spam. DNSBL Various email verification techniques. Various mail server verification techniques (ie. reverse lookup for PTR record). GeoIP filtering Email message content analysis Checking the number of "bad addresses" you are trying to send to Checking how many ...


4

Unfortunately, Microsoft guards their Junk Email filter like Fort Knox. Here is a link to a pdf that describes some interesting information about how the Junk Email filter works, but as the author admits, it's by no means documentation of the product. It's just his discoveries. As a developer, there isn't even a documented API for the Junk Email filter so ...


4

Barracuda does offer a VMware appliance. It is their Vx series. I just switched off of my 5 year Model 300 to Vx300 because my unit was crashing too much. This way, I don't have to come to the office to power cycle it. Barracuda Virtual Applicances


4

Have you looked at Postini(google bought it) as hosted spam prevention?


4

Exchange 2010 might allow using the domain/user/mailbox notation for accessing foreign user's mailboxes through IMAP. According to KB937359 this feature was originally removed from Exchange 2007, but re-introduced in SP1 Rollup 4. So it would be worth a try. There is also DavMail which might be of some help - it gateways standard internet mail protocols ...


4

You always need Spam and Ham samples. By only feeding Spam SpamAssassin refuses to activate the bayesian Spam filter. By issuing a spamassassin -D < /path/to/a/complete.mail you can check if bayesian filtering is activated or not (somewhere in the whole debug messages). Hopefully you didn't train SpamAssassin with old Spam (months old). It will only ...


4

None of them! Use just amavisd-new (with SA, without virus scanner!!) as before-queue-filter. You do it as described here: http://www.postfix.org/SMTPD_PROXY_README.html Even the pros and cons are extensively discussed there. Before you start you should have a look at http://www.postfix.org/POSTSCREEN_README.html to just drop 70% of all Spam before it gets ...


4

Get a VPS in a different country with less of a "reputation". Much of China's IP blocks, especially Hong Kong, will be treated with extreme suspicion for the forseeable future. There's nothing you can do about it. While I laud you for setting up SPF and rDNS, it's trying to make a silk purse out of a sow's ear. Also, check your IP at MXToolbox's blacklist ...


4

I outsource to Postini. I like Postini, but I am not necessarily advocating for them. I DO advocate outsourcing your spam filtering though, for three major reasons: It saves my bandwidth - MX records point to Postini, spam goes to them, they filter, I get ham. I don't have to waste server resources or bandwidth dealing with incoming spam. I don't have ...


4

Open powershell via the exchange menu item and run those commands: $list = (Get-ContentFilterConfig).BypassedSenders $list.add("mail@domain.com") Set-ContentFilterConfig -BypassedSenders $list


3

Hosted Environment Advantages: Managed by the hosting company Support is usually free/cheap If the hardware fails, they replace it If your company cannot afford or doesn't like paying for things all at once, payments are recurring rather than one big lump sum Hosted Environment Disadvantages: Service can cost more than an appliance in the long run If ...


3

From this research paper on SNARE, I present this nugget: For ham, 90% of the messages travel about 4,000 km or less. On the other hand, for spam, only 28% of messages stay within this range. My personal observations mirror yours and note that even now in 2014, geographic location continues to be an excellent predictor of spam. As others pointed out, ...



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