Here is a comprehensive list of what your email message goes through in order to get delivered:
- Virus Checks - The majority of virus (and worms) these days, travel around the internet by way of email messages. In order to protect valuable network systems from being attacked by a virus, most corporate networks and Internet Service Providers employ virus scanners that look for viruses and worms in much the same way that anti virus scans on your desktop computer. Most email server are set up to delete or quarantine any message that tests positive for a virus.
- SPAM filters and the huge growth of SPAM - Everyone hates SPAM! So much so, that people will change their ISP providers or email host to get better protection from SPAM. As a result, companies like AOL and MSN spend tons of money coming up with new ways to provide "better" spam protection to their subscribers to reduce their attrition rates.
- SPAM filtering methods:
- Phrase filters - watch what you say! Many email servers use a list of unacceptable or offensive word and phrase lists and will reject or place the message in a junk folder upon a match, so watch what you say, or your message could be rejected.
- Connection Checks - poorly configured email servers can cause loss of messages. This is most likely out of your control (unless you are a server admin), but just be aware that when email servers talk to each other, some are very picky about allowing a connection and may reject it if the source server does not "check out" properly.
- Statistical Analysis - this is used to catch some of the techniques used by spammers like many repeated words or a bunch of unrelated words stuffed in the message (usually to try to throw off the spam filters). Your message can become a victim of this if you do something like copy and paste a data file into the body of your message or if you were to insert a data file (like a mail list or spread sheet) into your message, as opposed to attaching the file.
- Domain Black Lists - Your ISP does not like your friend's ISP! - server administrators will use a list of trusted (and sometimes not-so-trusted) domain and/or IP address lists to filter incoming messages. If you happen to be using one of the "bad" service providers, your messages could be dropped. Watch the company you keep!
- HTML code checking and filtering - Don't get too fancy with your Html email messages. Many servers are set up to reject messages that contain certain html code. Especially scripts, deceptive URLs or encoded text.
- Discretionary Blocking by email address, domain, or IP block. - Most email server gives the admin the power to place a block in their server to deny access to any server or domain of their choosing.
- Server Rule Sets - in addition to all of the above obstacles, most email servers can be custom configured with rules that will redirect or delete messages on just about any content that you can think of! A incorrectly coded rule could create a virtual sink hole for messages.
Now, assuming your message gets through all of the above checks, the next pitfall is in the email client program, like Outlook.
- Email Client Rules and Filters - Just like servers can have rule sets that redirect or delete messages, most email client software also has the ability to create custom rules to delete or move messages into a folder. Again, an improperly coded rule could create a black hole for your message.
- Unsolicited Message Filters, or Junk Filters - Most email client software also provides some sort of Junk mail filter, like Outlooks Junk E-Mail filter and add-on filters like SpamAssassin. These filters have become quite reliable, but there is still a small percentage of False Positives that will occur. Your message could fall victim to one of those false positives.
Other pitfalls:
- Standards not adhered to - Although there are sets of standards (RFCs) that software providers and administrators of server are supposed to abide to, the standards are many times loosely adhered to. In fact most email server software gives the admin the option to turn on or off specific RFC features at their will or desire.
- False Positives - virus and spam filters. - Every content filtering technology has a certain percentage of False Positives that are considered acceptable.
- Proprietary Systems - There are many home grown systems out there that are simply poorly written and do not conform to standards.
- The Wild Wild West... everyone configures their systems based on their view, morals and opinions.
- Quotas - Sorry, that mailbox is full - Many service providers will limit the size of your inbox. The reasons for this are obvious... storage costs money.
- Daily Delivery... no so much! - Just because your message got through today, does not mean it will make it tomorrow. Content and virus filters are often updated daily. Also, the little geek behind the server administrators console may decide to add an additonal filter or click on a new feature just to try it out (I know, I've done it)... again, it's the Wild Wild West.
So, how can I Fix this? What can I do?
- Mostly, be aware of this.
- Request a "Delivery Receipt". Most email clients support this, however, most email clients also provide the option to ignore them when received. Still, it does not hurt to ask!
- Request a confirmation. Ask the recipient of the message to reply back to you with confirmation that they received it. This is probably the most reliable method of making sure the message was received.
- Assume Nothing - never simply assume that the message was received. You know what assuming does... It makes an ass out of you and me!
- Follow up. If the message is critical, follow up with a phone call, or with an additional email requesting a confirmation.
The Result and my recommendation:
Email is a great and very convenient for daily communications, but just be aware of the pitfalls and do not over rely on email for critical communications. And please... Don't send your critical business files via email. FTP or burn on CD and send overnight.
