Antispam filters
What are antispam filters?
Antispam filters, or junk email filters, are applications used to stop spam from reaching email inboxes. They are not infallible, but they prevent users from seeing their inboxes flooded with spam.
The way users behave when they receive emails helps filters learn and improve their performance. Together with the constant updating of RBLs (blacklists of junk email senders), this makes the criteria for classifying emails as spam increasingly precise.
On the other hand, each company can add its own rules to its antispam filter so that, locally, the accuracy of spam detection is improved.
What can you do to get past antispam filters?
There are no magic formulas for getting your emails past antispam filters, but what you can do is follow these tips so that antispam filters have a better perception of the emails they receive from your domain:
- At DNS level. You must have your DNS correctly configured, with at least the SPF, DKIM and DMARC records. Also leave your domain registration data visible in WHOIS queries.
- Don’t use purchased databases. Always use double opt-in lists or, failing that, opt-in lists, to prevent recipients from marking you as spam, since spam complaints cause antispam filters to block you.
- Take care of the subject line and content. Don’t write all the text in capital letters and avoid suspicious words or phrases, such as: free, gift for you, opportunity, etc. This makes antispam filters much more likely to block you.
- Send with a quality infrastructure. Sending a single email and sending an email marketing campaign are very different things, so rely on a quality email marketing platform such as Mailrelay.
- Avoid sending attachments. When an email with an attachment arrives, the antispam filter has to analyze not only the subject line and content, but also the attachment itself, which greatly increases the chances of it being flagged as spam.
- Include an unsubscribe option. If you send email marketing campaigns, always give subscribers an easy way to unsubscribe in a visible place; this will save you a lot of spam complaints.
- Don’t use URL shorteners or paste URLs directly. Using URL shorteners gets your emails penalized and sent to spam, because it is interpreted as an attempt to hide the destination page. Also, don’t paste URLs directly into the text; use text links instead and you will avoid being penalized.
- Segment and send. A well-maintained database is very valuable, so segment it and update it frequently. You also need to keep it free of spamtraps and remove hard bounces.
- A design with images and text. The design should never be just an image; it must contain images and editable text. Likewise, avoid embedding text in images, as this is often interpreted as an attempt to hide the text from antispam filters.
How can you fool antispam filters?
If you’re thinking of fooling antispam filters, it’s only fair to tell you that you’re highly unlikely to succeed. It isn’t impossible, since your own antispam system has let spam through to your inbox at some point, but it isn’t within everyone’s reach.
If you choose to fool them… and you succeed, it will backfire on your future sends: once you are detected, the filters will learn from it and may block you from the servers where they are active for good.