It Never Happened Before!
Often, we are asked, “I sent an email to someone that I have been emailing for years and it got blocked by their spam filters. Why?”
Or….
“I sent an email to someone and when they replied to me, my spam filters identified them as spam. Why would it do that when I sent the original email?”
Unfortunately, email spam filtering is not as simple as having had regular communications with someone for years or being the original sender. If it were, all of our lives would be a whole lot easier. There are many issues that can contribute to being identified as spam. This article attempts to address some of them.
First, it is important to understand that there are many different spam fighting techniques. Everything from RBLs (filtering based on network addresses) to Challenge/Response (software that requires a sender verify that they sent an email) to Content Filters (software that analyzes the body/content of email messages). This article addresses issues that arise from content based filters.
Some types of content based spam filters will parse through an email message looking for characteristics common to spam. Any characteristics the filter identifies will be given a score. All scores will be tallied and if the total is greater than a predetermined threshold, the message will be identified as spam and processed according to the rules configured by the user or the server administrator.
So, what does this have to do with you?
Spam Filters On The Move. You may unknowingly have characteristics in your emails that are similar to spam. These characteristics may not amount to enough to identify your emails as spam….. Yet. However, given the fact that spammers are constantly changing their tactics in order to slip past filters, spam fighting software is also being modified constantly to address new spamming techniques. When spam filter software gets updated, which is happening a lot, the criteria used to identify spam is likely being modified. Depending on the changes made to the software, you could, for example, send an email to someone one day, without being identified as spam and, the very next day after the software was updated, send the exact same email message and have it identified as spam.
Emails Are Like Snowflakes. It is important to remember that every single email that is sent is unique. Even if you are replying to an email that was sent to you, that reply email will be analyzed as if it were received for the first time. And, in fact, it is being received for the first time no matter how many replies back and forth. Just because you have had a few successful email deliveries in a “threaded” correspondence, does not “grandfather” you past the filters. More likely, if you leave the content of each email exchange in your email replies, the spam filters now have more content to consider, often resulting in higher spam scores.
Don’t Count On Residential Email Service. Many people use their residential email account (Yahoo, Hotmail, Comcast, Verizon, etc) for business communications. These types of email services do not seem to take deliver-ability of business email into consideration when implementing spam filters. They are often only concerned with stopping the flow of spam. As such, they often implement very strict spam fighting techniques that end up slowing or stopping altogether the flow of legitimate email. Furthermore, obtaining support from these types of companies for spam related issues is typically about as easy as wrestling a whale. We suggest not using residential class email services for mission critical, business email.
So, what to do? When dealing with content based spam filters, the easiest thing to do is use your whitelist. Simply put, a whitelist is a list of email addresses that are granted safe passage past your spam filters. Usually, you should have control over your whitelist and we suggest that you add email addresses to it that you regularly communicate with and ask them to do the same. Other than a whitelist, we suggest:
- Configuring your email client to compose in plain text versus HTML
- Remove any images you may have in your email
- Remove links form your email
- Avoid using email to transfer documents
