The increasing use of filters by companies to block spam has a downside for law firms engaged in legitimate email marketing — an increased risk that their e-mails will be improperly labeled as spam and either blocked entirely or routed to users’ junk (bulk mail) folders and never read. The risk of legitimate e-mails getting filtered has spurred interest in deliverability — that is, solutions to maximize the delivery of e-mail campaigns to intended recipients without getting blocked.
This post reviews the different types of filtering (e.g., content filtering, IP address filtering), and explores email newsletter deliverability solutions to address each (e.g., automated content checking, private IP addresses, and custom domains).
Filter Type 1: Content Filtering
Content filtering continues to be used by anti-spam software systems. These systems analyze the contents of an email header, subject line and body, and assign “points” for the use of certain phrases or HTML code commonly used by spammers. Emails whose “points” exceed a pre-determined total get blocked.
Content filters penalize emails for using common “spam” phrases such as "work from home" or "guaranteed income", but may also assign points for such innocuous phrases as “free” or "click here,” and thereby cause otherwise legitimate emails to be blocked. The filters also assign points to text formatting such as the use of ALL CAPITAL LETTERS, excessive use of bright colors, or very large fonts that even legitimate emailers may use. The filtering companies assemble all of these text and formatting “triggers” into a dictionary that can be used by mail servers to examine incoming email traffic.
Solutions to Content Filtering
It’s important to remember that just because your email contains a “trigger” word or certain formatting does NOT mean it will be blocked. It is the accumulation of multiple “triggers” that causes the points assigned to your email to exceed the threshold that will cause blocking to occur. At the same time, in order to minimize the risk of filtering, it is a good idea to eliminate any unnecessary “triggers” that are not essential to your message. To this end, legitimate emailers should use email marketing software that automatically runs an email subject line and body against the dictionary used by ISP’s and corporations to filter emails, alerts users to any problematic text or formatting that is likely to trigger filters, and then recommends a resolution to each identified problem before the email is sent.
Filter Type 2: List Quality Filtering
Many spam lists contain a large number of bogus addresses and therefore spammers "bounce" a lot of mails. To combat this problem, many ISP's and corporate domains have added list quality filters to detect when a large percentage of email addresses being used by a sending domain are bad. If the volume of bounces from a particular domain exceeds a certain quantity, all other emails from that source may be blocked.
Solutions to List Quality Filtering
Any solution that reduces the number of “bounces” from invalid addresses will improve the quality of your list and thereby increase the deliverability of emails to valid addresses.
To this end, many email providers will stop sending emails to addresses that “bounce” – i.e., are identified as “undeliverable” - one or more times. Importantly, not all bounces are created equal. A “hard bounce” is an email address that is undeliverable for reasons that are likely permanent such as “address invalid” or “domain not found.” In contrast, a “soft bounce” is typically undeliverable for a temporary reason, e.g., “mail server down” or “out of office.” An email address that “hard” bounces will typically be removed from a list immediately while an email address that “soft” bounces may be included in future distributions and only removed after 3 undeliverables.
Removal of bounced addresses from your distribution list will improve your reputation with ISP’s and also decrease your email volume fees (since bad addresses won’t be included in your total send figures with the provider).
Filter Type 3: Volume Filtering
Since many spammers send bulk emails without regard to their accuracy or volume, many ISP's and corporate domains filter using volume based filtering. Volume filters focus on the number of simultaneous connections that are opened at any one time from a particular sending domain.
Solutions to Volume Filtering
To avoid triggering volume filters, some providers will monitor the number of connections opened (known as threads) at an ISP domain at any one time. This ensures emails are delivered at a maximum rate without triggering volume filters at large ISP's such as AOL or Yahoo.
Other vendors will stagger delivery of emails to avoid volume triggers. This is called “send throttling.” The distribution will take longer but the delivery rate will be higher.
Filter Type 4: IP Address Filtering
Blacklists
A black list is a list of IP addresses and domains of e-mail servers known to send spam. The black list is used to block all e-mail that comes from those servers. The problem is that a blacklisted email server may also be used to send legitimate email.
There are numerous active blacklists in use today, some maintained by private companies and individuals, and some operated by anti-spam organizations such as SpamCop.
Reverse Lookups
Other organizations perform what is known as a reverse DNS lookup on incoming emails in order to catch spammers. All legitimate IP addresses should be traceable back to a legitimate domain name; if an IP address is not traceable, then that might indicate the email was sent by a spammer who is trying to disguise the origin of his message.
Solutions to IP Filtering
Whitelists
The opposite of “blacklisting is “whitelisting,” which is the creation of a list of “legitimate” IP addresses, domains and/or email addresses that are deemed “trustworthy” by a receiving domain. Emails bearing a whitelisted IP address, domain or email address will avoid filtering and be delivered directly to the recipient.
There are numerous ISP-specific and industry whitelists. It would be wise to choose an email service provider that participates in leading whitelisting programs. For example, AOL offers accredited email service providers access to a program under which providers agree to automatically unsubscribe any AOL subscriber from a list after the subscriber clicks the “Report Spam” button in AOL. Because automatic removal reduces the potential for abuse, this solution allows AOL to continue delivering emails sent by participating vendors to AOL customers even where certain emails sent by those vendors were previously designated as spam.
Another important “whitelist” is the Email Accreditation Database maintained by the Institute for Spam and Public Policy. Email service providers accepted into this database can offer email marketing clients increased credibility with a host of filtering and anti-spam organizations such as Postini, SpamCop and Outblaze.
Sender Authentication
Some organizations have deployed mechanisms to authenticate the origin of emails, i.e., verify that a message that says it’s from Citicorp is, in fact, from Citicorp. These mechanisms are designed to thwart “phishing,” that is, a technique by which a spammer “spoofs” the identity of a legitimate organization such as Citicorp or eBay. Examples of authentication frameworks are Sender ID (employed by Microsoft platforms such as Hotmail) and Domain Keys (used by Yahoo). Email service providers typically provide support for these authentication tools if requested in order to improve a client’s deliverability to certain domains (such as Hotmail or Yahoo).
Goodmail
Goodmail CertifiedEmail service is a new service that embeds a cryptographically-secure token in an email to verify its authenticity. Participating receiving domains such as Yahoo can detect the token, allow the message to bypass content and volume filters, and deliver it to the recipient’s inbox where it is distinctly labeled with the CertifiedEmail trust symbol, indicating that it is from an authentic and trusted sender and can be opened with confidence. Because a Goodmail authentication “seal” is essentially a “stamp of approval,” Goodmail applies strict screening criteria before accepting an email service provider into its program. The downside is that a sender has to pay a small fee per email for the privilege of the seal, which can get expensive at high volumes.
Private IP Address
A premium deliverability option offered by some vendors is a private IP address for individual clients – that is, an IP address used only by that client to send email and not shared by any other client. The user of a unique IP address is thus insulated from the potentially compromising email practices of outside parties.
Custom Domain
A custom domain provides clients of an email service provider with a unique domain name for all of the relevant email addresses used in an email header – e.g., bounce address, reply to address, etc. This solution enables an email to pass various reverse “lookup” tests frequently run by mail servers to verify the authenticity of a particular domain and match it up with a valid IP address.
The bottom line is that e-mail remains a viable and successful channel for reinforcing the expertise of a law firm, communicating important developments and news to clients, and identifying client interests, concerns and needs. However, to achieve these benefits, a firm’s e-mail must avoid filters and get delivered to the inboxes of the intended recipients. If you suspect your e-mails are getting filtered, it may be time to consider an email service provider that can offer some of the deliverability solutions described in this article.
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