Uncategorized, computer security, domain maintenance, email support, Spam filter

Undeliverable: Why are some emails blocked?

Email and blacklists are hard to make sense of.

Spam filters sort through inbound and outbound mail. If you have a spam filter on your network, when an email is sent, the spam filter checks the domain against a known blacklist. If the domain is not on the list the email goes out.

Let’s say you send email to joe@fiddle.com. Your email server sends this out to a place on the internet. The internet has records that say where to go. We call these MX records for Mail Exchange records.

Now if the receiving server in this case fiddle.com gets a message from you it checks to make sure you are not a known spammer.

How do email addresses get on a blacklist?

Here are a couple ways an email address can be added to a black list.

  1. Someone has a virus on their network and is sending out spam.
  2. They have changed an email host or setting that causes a problem with the configuration.
  3. They could have received a new IP address and this was actually on a blacklist.
  4. A Domain Name System or DNS list could have picked them up and put on a blacklist.

The domain blacklist to correction time is generally pretty quick.
If your emails are being returned as undeliverable, contact us!

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