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Threats to Email Delivery

Mark Edwards
22-11-2003

As the volume of spam increases IT Managers use an increasing array of tools to reduce the volume of unwanted messages entering their corporate mailservers. The larger the corporation the larger the volume of junk mail they have to contend with and the more draconian the solutions they need to apply to deal with the problem. For those of us who send legitimate emails, the instance of emails not being delivered for various reasons is increasing.



Here is a list of some of the tools being used to protect corporate mailservers:



Content Filters - These are perhaps the most pervasive threat to email delivery. These filters rely on a list of keywords in the content of the message to identify spam. The list of words triggering rejection is getting quite difficult to avoid, for instance, funny and guarantee.



Blacklists - Some ISPs check against these global lists of known spammers by looking at the headers of your emails for the IP address that it was sent from. Some of these blacklists block an entire range of IP addresses when they find instances of spamming meaning that legitimate businesses end up black listed simply by using the same hosting company as a spammer. Many also regularly check IP addresses to ensure it is not an open relay that anyone can use to send email or whether the IP address matches the domain name.



Volume Filters - Certain large ISPs use these filters to identify and block spam. If more than a threshold number of emails is received from the one sender within a set period of time the message is then regarded as spam and blocked.



Bounce Removal Checking - Yahoo, amongst others, records continuous attempts to deliver email to non-existent addresses. If you keep trying to email the address instead of removing it from your list, all email you send to Yahoo may be blocked. Thus, you should remove undeliverable addresses promptly.



Mail Servers with dynamically assigned IP addresses - In April 2003, AOL blocked email traffic from all mail servers of this type which affected a lot of legitimate home based business mail servers.





So if you plan on sending client emails you should contact us about providing solutions which provide maximum delivery of your communications.

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