Electronic mail commonly known as e-mail has permeated most of the fields nowadays providing a way for communication for people from every corner of the world. Through the passage of time, electronic mailing has extended its significance to the business world. And today email is one of the fastest growing means of communication for business to business transactions and business to customer as well.

Online marketers maximize all the resources at hand to optimize their mailings - from the appearance of the email to its content, and many more. Unfortunately emails can get block regardless of the effort done in sending it. Basically there are two common reasons why legitimate emails (e.g. opted in promotional, newsletters) get block. During peak hours (time when most emails are sent), ISP's get overwhelmed and thus experience a temporary technical problem which disables them from sending emails. False positive is another reason why emails are not delivered to prospects' inbox. False positive occurs when a legitimate email is flagged as spam and thus redirected to bulk folder instead of having it to the inbox.

In a content based filter, the software looks on the subject line, header, and content of the message which appear suspicious. The filtering process is very dependent to phrases and words chosen by the user as spam, this means that spam messages with words or phrases not included in the list of the user will make it to the inbox time and again unless the user creates another filter to deal with those words and phrases. The good side of this filter is, it can be fashioned in anyway the user wishes to.

Content Filter is just one type of filter. There are also Bayesian filter, volume-based filter, and etc. In addition, major ISP's use blacklists (lists of IP addresses of known spammers). Blacklists are not 100 percent accurate, because some the IP addresses included on it don't send spam.

Blocked legitimate emails are difficult to track. Once an email is sent, online marketers have no means of knowing if the email was sent to the recipients, not unless bounced emails are generated. And since content filters just redirect email to bulk folders, no bounced message is sent to the marketer indicating that the message did not reach the inbox.

I believe it's time to make every email count. If you think your emails do not reach your prospects inbox, in that you get few responses from your emails, you better procure an email delivery assurance system. The said system can help you track which ISP's and filters are blocking your emails and help you fix the problems that keep your emails from your prospects' inbox.

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