January/February 2011

How It Works: Where's My Mailing?

By Raederle Clay

As enewsletter circulation and promotion increase, mailing delivery speeds become more of a concern.  The most common questions that iProduction Customer Support receive are, "Mailzeen says it's still 'Distribution in process,' is it really still going out?" and, "Mailzeen says it's complete, but I haven't received it yet."  To address both of these questions, here is a brief overview of how the mailing process works.

Once the mailing is scheduled and approved, it goes through a staging process in which the data for the mailing (all of the users' email addresses and the content of the mailing) are gathered in a single location so the distribution server can assemble each recipient's message.  The distribution server assembles all of these individual messages and transfers (distributes) them to the delivery server, which is the server that actually makes the connection to the users' receiving servers and passes the message along (delivery).

Common situations that can delay distribution include large mailing lists and multiple mailings for a site going out at the same time.  Think of assembling a large mailing list like moving: the more possessions you have, the longer it takes to put them in boxes; the more boxes you have, the longer it takes to carry them out to the truck.  Multiple mailings going out is be like having two people in the same building moving at the same time: they each have to wait for the other to unload the elevator before they can use it.

Whenever possible, we recommend a staggered schedule for mailings, especially when sending multipe mailings together.  Our distribution system is rated at 100,000 messages distributed per hour, so a list of 50,000 normally takes approximately 30 minutes to deliver.  However, this rate may vary depending on the total amount of activity occurring at any given time; in the early morning or late evening hours, mailings often distribute more quickly while mailings sent during peak hours (mid-day) may distribute more slowly.

The most common cause of delayed delivery of a mailing is throttling by the user's receiving server.  Throttling (sometimes called "deferral") is an action taken by the receiving server to manage spam or their own hardware limitations and is often IP-based.  Three common triggers that may prompt a receiving server to throttle messages are (note: all thresholds are defined by each provider and may vary among providers):

  • Transaction threshold limit exceeded (too many connections made at the same time)
  • Recipient limit exceeded (too many messages sent to that domain at the same time)
  • Message size limit exceeded (too much data in the mailing making its file size too large)

In cases where the messages are deferred, this can back up on the delivery server and put a strain on the resources available for mailing delivery.  In light of the significant increase we have seen in the number and volume of mailings over the last year (which also increases deferral rates), we have made some hardware adjustments to our delivery servers.  However, we welcome calls to verify the status of a mailing; we can even quickly determine whether a message to a specific user has been delivered or is being deferred.