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Understanding delivery at the server level

When you send a mailing, the response tracking that begins is actually happening at two distinct levels: the server where your recipient's inbox is hosted and managed, and the inbox itself.

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On the Response page, you can view the following types of mailings: In progress, Sent and Automated. Click the name of the mailing, or in the dropdown menu to the right of the mailing's name, choose View response.

Emails sent, received, in progress and bounced all happen at the server level when we receive certain codes (and messages to go with them) back from the receiving servers. Beyond that initial level of tracking, the receiving servers control much of what happens from there. They decide whether to deliver emails immediately on to recipients or to run them through a filtering program of some sort. And, like any server network, they occasionally experience problems like too much traffic, viruses or overflowing inboxes.

Numbers of recipients

The number of emails we attempted to send

Each mailing you send takes just a few minutes to prepare before heading out the door. During this brief window of time (often just a few seconds), your mailing will display as building on the "In progress" tab of the Response page. If you've waited a few minutes and still don't see your mailing listed under the "In progress" section, it may not have gone out. Check in with us to be sure before attempting to send again.

If you selected a group of 1,000 people to send your mailing to, then the number of recipients will be 1,000. Remember that we're only going to attempt to reach the Active members of an audience group, not members in Error or Opt out status, and that your totals for successful delivers and bounces may take up to 30 hours to fully tabulate. That's because we're continuing to try to reach people over a period of hours if the first several attempts fail. Once your mailing has completed, the response will display on the Completed tab of the Response page.

Successful deliveries

The number of emails that did not hard or soft bounce

When an email is delivered, the server that receives it provides us with a response code. The codes tell us if the email was successfully accepted, rejected because of a network or inbox problem or bounced back because the email was deemed unfamiliar or unwanted. There is a standard set of response codes, and most servers are good about using those codes in the right way. At that point, we're relying on the server to finish the delivery job and pass the email on to its intended recipient.

For that reason, it's entirely possible for an email to be received by the server but never reach a recipient's inbox. Because many servers and networks incorporate filters to help decide which emails get delivered and which do not, it's important to closely monitor things like bounces and other response metrics and to make sure you're adhering to our very high standards of permission-based email marketing.

Emails in progress

The number of emails currently in line to be sent or retried

You may see emails in progress for up to 30 hours, as we make follow-up delivery attempts every 30 minutes to addresses whose servers may have been busy, down or unresponsive on our first try.

Any email addresses still bouncing after four attempts will be marked as a soft bounce, and your mailing's delivery will be complete. An address that soft bounces will remain an active contact in your audience unless it soft bounces four consecutive times, when it will be moved to Error status and not included in future send-offs.


Emails that were kicked back as undeliverable by the receiving server

Before an email can reach someone's inbox, it has to be accepted by the host server. Bounces occur when the SMTP transaction between our mail server and your recipient’s mail server fails.

The error codes given at the time of might be standardized at each organization, but they can be quite different from provider to provider.

There are two main categories for bounces:

  1. Soft bounce (a three-digit response code starting with a 4) – A temporary failure due to an outage, full mailbox or other issue that should resolve itself. Soft bounces are considered temporary, so delivery is reattempted over a 30-hour period before giving up on reaching the receiving server. This can happen for four mailings in a row before we will move the address from Active to Error.
  2. Hard bounce (a three-digit response code starting with a 5) – A permanent obstruction to email delivery, such as a nonexistent email address, a block due to a content or the server is rejecting your email as junk mail. Hard bounces are deemed invalid and moved to Error status. They won't be emailed to again unless you re-activate them.

If you feel an email address is inaccurately displayed as an error or notice a delivery problem with an ISP, please reach out before reactivating that address or taking action to resolve a delivery problem. We’ll gladly investigate the Error status of any recipient or group of recipients and help restore addresses for you, and we'll work directly with ISPs and blacklists to resolve sending issues quickly.

For reference, we've compiled error code help documentation by ISP/company. We don't manage or monitor these sites, but they can be helpful if you're trying to track down the reason for a bounce:

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