Last Updated on Monday, 28 December 2009 11:48 Monday, 13 April 2009 17:00

Q: Why does it take so long for me to get emails from someone after they tell me they sent it?

A: There are a lot of factors that can cause one email to get to you much more quickly or slowly than another email. Here's the process an email goes through to get from point A to point B:

When someone sends an email, their email client puts it into an outbound queue. Depending on the email client, that email may or may not be sent right away. Some email programs will send every email immediately when you click Send, others will actually send it along with any others the next time the email program sends and receives emails to the server, and the delay in that queue can be from one to sixty minutes or more. After it is sent from their computer to their mail server, it goes into another queue for handling by the server. If that server is not the main mail exchanger, it may go from that mail server queue to any number of other mail server queues until it reaches the main mail exchanger queue.

That server will look up the Mail eXchanger (MX) record for the domain (like netfu.com) of the receipient's email address. That record tells it what server to send the email to, which it will use to send the email. If that server fails to respond or to take the email, the sender's mail server will look up the next server in the list of MX records until it successfully sends the email to one of them. The recipient's domain may have one or two MX records, dozens, or even hundreds. Each connection can take up to a minute for the servers just to begin to talk to each other, since it can be affected by networking errors, spam lookup lists, etc. After communication is established, the server begins sending the email, along with any other emails it has for the same domain. Only after all the emails for that domain are transferred can they be handled by the receiving mail server, so the total size of all the emails can affect this step.

At this point, the email is in the queue of one of the main mail exchangers for the recipient. From there it may be delivered directly to the recipient's inbox or it may have to be delivered to any number of mail server queues. Once it is delivered to the mail server queue on the server responsible for the recipient's email, it will actually be delivered to the recipient's mailbox once the server gets to it. At that point, depending on the recipient's mail client setup, he may see it, or he may have to wait for his mail client to check with the server to get it.

There are many points in this process where an email can be stopped for longer than normal, especially depending on the volume of mail and capabilities of the server. A good way to troubleshoot this process is to have the sender send an email with the sent date and time manually typed into the email, then look at the email and its date/time at the recipient when it is received. Most, but not all, mail cients will display the date/time the email was actually received at the recipient's mail server when you see the email in a list with other emails. When you open the email, again depending on the mail client, it may display the date/time the sender sent the email or the date/time it was received by the recipient's mail server again. Regardless of the mail client, the detailed dates and times in every email's Full/Internet Headers can help to troubleshoot email delays and find the cause.

If the sender's typed date/time is very close to the email's date/time as listed in the recipient mailbox, but the email was received much later, the problem lies somewhere between the recipient's mail exchanger and the recipient's computer. However, if the typed date/time is much earlier than the email's date/time as listed in the recipient mailbox and the recipient received the email close to that time, the problem lies somewhere between the sender's computer and the recipient's mail exchanger.

Of course, all of this depends on the dates and times of the servers and computers involved being as close to correct as possible.