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39

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 ...


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

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

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 ...


6

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 ...


6

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

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

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

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

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

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 ... ...


4

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 ...


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

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

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 ...


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

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

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 ...


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

I worked in Support there for nearly 2 years and OP is definitely correct. BSF 100-400 use desktop quality HDD. The RMA rate was through the roof. I would avoid purchasing any of these units like the plague. Note: This HDD practice is not limited to the Spam Filter but all lower end products the make. tl;dr: Get amavisd, spamassasin, and clamd and some ...


3

There are several options to accomplish this, and they all largely depend on the delivery agent you are using to do the final delivery to a user's virtual mailbox. If you are using the stock Postfix virtual(8) delivery agent, you can't accomplish this. If you are using either the Cyrus LDA or the Dovecot LDA, you habe two more options: You can either use ...


3

Regarding the HTML_IMAGE_ONLY_24: HTML: images with 2000-2400 bytes of words This means that it has an image of 2k - 2.4kb - it means its a very small image which can indicate spam. The BSF_ obviously stand for Barracuda Spam Filter and are custom rules from them. The SA392f is most likely an internal rule code from them. This is their "value add" to ...


3

SoaperGEM is correct. It has nothing to do with the size of the image. Barracuda wants to see a certain amount of text content. If you don't have 2000-2400 bytes of actual words and you have an image, you're screwed. Also, Barracuda will not tell you anything about their custom rules, which is frustrating but understandable (trust me I've tried). How ...


3

Sendmail is evil ;) One solution could be to install SpamAssassin and integrate it with spamass-milter into your mail services. This has the advantage that you could activate lot of other Anti-Spam rules. Or just write your own plugins which is really easy.


3

If you're running postfix as your MTA, configuring the right DNSBLs is 90% of the solution :) Also, since you say you're upgrading to latest versions, you will appreciate postfix' new SMTP triage server, postscreen. It handles all RBL checking in parallel, and has an extensive black- and whitelist cache, thus easing the load on the parts of the system that ...


3

If you have to ask for how to guides - you should not be doing this for any "clients". From your question it seems you do not understand what spamassassin is or how it works. It is a milter (mail filter). The messages to check for SPAM get passed to it by your MTA. How to configure it properly depends on the MTA you use.


3

Does rDNS pull the IP address from the Received: portion of the header Depends on exactly what you are looking at. A mail server, or some anti-spam system. Most often the IP address used has nothing to do with anything in the message headers or body, and instead is the source address of the mail server/client that has connected and is attempting to ...



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