While there are many methods by which email messages can be blocked (for example, DNSbl listings can results in IP addresses being refused connections, subject lines could match previously seen spam, or URLs or email addresses in the body might trigger a receiver's content filters), there is one main reason that filters to the top when you consider
why an ISP or anti-spam company blocked or bulk-foldered a given email message:
- end-users have complained, in volume, about your email, or other email from your IP address
It is that simple. ISPs and anti-spam filters take steps to block mail because their users tell them it's unwanted. They are not blocking email
because they don't like you. Senders of all sizes need to be aware that ISPs are paying much more attention now to the behavior of their users and, when their customers say "we don't want this mail", it has real meaning. As noted, in part, in
this blog post by Laura Atkins at Word to the Wise, ISPs and deliverability experts have been saying similar things for quite some time. Keeping your recipients engaged and making sure that what you're sending is wanted and requested
before you send it goes a long way to making sure it makes it into the inbox. Also - once a user tells you they don't want your mail by unsubscribing, don't send them more mail! It seems obvious, but it's happened more than once, and one of the worst things that you can do to your reputation is accidentally send mail to your suppression list.
Something else to consider - the concept of "end-user complaints", for many ISPs and anti-spam filters, also includes email messages sent to long-dead addresses or to addresses that have never existed. If an email address has been dead, and the ISP has been sending you "no such user" or "invalid recipient" bounces, for the last few months and you're still trying to send to it, that's going to put your acquisition and retention policies in doubt, and the reputation of the rest of your email will sink. Al Iverson with Exact Target talks a bit about that in
this post. The takeaway here is that maintaining a mailing list is more than just acquiring addresses - it's making sure with that you respond quickly and appropriately to
every unsubscribe request or bounce message you receive for
every mailing you send out, it's making sure that you are proactive in determining why your recipients don't want your mail and taking steps to make sure they
do want it, and it's nurturing your relationship with your recipients.
