You want your recipients to read your emails, find them valuable, and not
label them as spam. In other words, you want to maximize email
—the percentage of your emails
that arrive in your recipients' inboxes. This topic reviews email
deliverability concepts that you should be familiar with when you use Amazon SES.
To maximize email deliverability, you need to understand email
delivery issues, proactively take steps to prevent them, stay informed of
the status of the emails that you send, and then improve your email-sending program,
if necessary, to further increase the likelihood of successful deliveries.
The following sections review the concepts behind these steps
and how Amazon SES helps you through the process.
Understand Email Delivery Issues
In most cases, your messages are delivered successfully to recipients
who expect them. In some cases, however, a delivery might fail,
or a recipient might not want to receive the mail that you are sending.
Bounces, complaints, and the suppression list are related to these
delivery issues and are described in the following sections.
If your recipient's receiver (for example, an ISP) fails to deliver
your message to the recipient, the receiver bounces the message back to
Amazon SES. Amazon SES then notifies you of the bounced email through
email or through Amazon Simple Notification Service (Amazon SNS), depending on how you have your system set up.
For more information, see
Monitoring Using Amazon SES Notifications.
There are
hard bounces and
soft bounces,
as follows:
- Hard bounce – A persistent email
delivery failure. For example, the mailbox does not exist. Amazon SES
does not retry hard bounces, with the exception of DNS lookup failures.
We strongly recommend that you do not make repeated delivery attempts to
email addresses that hard bounce.
- Soft bounce – A temporary email
delivery failure. For example, the mailbox is full, there are
too many connections (also called throttling),
or the connection times out. Amazon SES retries soft bounces multiple times.
If the email still cannot be delivered, then Amazon SES stops retrying it.
Amazon SES notifies you of hard bounces and soft bounces that will no longer be
retried. However, only hard bounces count toward your bounce rate and the bounce metric
that you retrieve using the Amazon SES console
or the
GetSendStatistics API.
Bounces can also be
synchronous or
asynchronous.
A synchronous bounce occurs while the email servers of the sender and receiver are actively
communicating. An asynchronous bounce occurs when a receiver initially accepts an email
message for delivery and then subsequently fails to deliver it to the recipient.
Most email client programs provide a button labeled "Mark as Spam," or similar, which
moves the message to a spam folder, and forwards it to the ISP. Additionally, most ISPs
maintain an abuse address (e.g., abuse@example.net), where users can forward unwanted
email messages and request that the ISP take action to prevent them. In both of these
cases, the recipient is making a complaint. If the ISP concludes that you are a spammer,
and Amazon SES has a feedback loop set up with the ISP, then the ISP will send the
complaint back to Amazon SES. When Amazon SES receives such a complaint, it forwards
the complaint to you either by email or by using an Amazon SNS notification, depending on
how you have your system set up. For more information, see
Monitoring Using Amazon SES Notifications.
We recommend that you do not make repeated delivery attempts to
email addresses that generate complaints.
The Amazon SES
suppression list is a list of recipient
email addresses that have recently caused a hard bounce for any Amazon SES customer.
If you try to send an email through Amazon SES to an address that is on the suppression
list, the call to Amazon SES succeeds, but Amazon SES treats the email as a hard bounce
instead of attempting to send it. Like any hard bounce, suppression list bounces count towards
your sending quota and your bounce rate. An email address can remain on the suppression list
for up to 14 days. If you are sure that the email address that you're trying
to send to is valid, you can submit a suppression list removal request. For more information, see
Removing an Email Address from the Amazon SES
Suppression List.
One of the biggest issues with email on the Internet is unsolicited bulk email,
or spam. ISPs take considerable measures to prevent their customers from receiving
spam. Correspondingly, Amazon SES takes proactive steps to decrease
the likelihood that ISPs consider your email to be spam. Amazon SES uses
verification, authentication, sending limits, and content filtering. Amazon SES
also maintains a trusted reputation with ISPs and requires you to send high-quality
email. Amazon SES does some of those things for you automatically (like content
filtering); in other cases, it provides the tools (like authentication), or guides
you in the right direction (sending limits). The following sections provide
more information about each concept.
Unfortunately, it's possible for a spammer to falsify an email header and
spoof the originating email address so that it appears as though the email
originated from a different source. To maintain trust between ISPs and Amazon SES,
Amazon SES needs to ensure that its senders are who they say they are.
You are therefore required to verify all email addresses from which you send
emails through Amazon SES to protect your sending identity. You can verify
email addresses by using the Amazon SES console or by using the Amazon SES
API. You can also verify entire domains. For more information, see
Verifying Email Addresses in Amazon SES
and
Verifying Domains in Amazon SES.
If your account is still in the Amazon SES sandbox, you also need to verify
all recipient addresses except for addresses provided by the Amazon SES mailbox simulator.
For information about getting out of the sandbox, see
Moving Out of the Amazon SES Sandbox.
For more information about the mailbox simulator, see
Testing Amazon SES Email Sending.
Authentication is another way that you can indicate to ISPs
that you are who you say you are. When you authenticate an email, you provide
evidence that you are the owner of the account and that your emails have not been
modified in transit. In some cases, ISPs refuse to forward email that is not
authenticated. Amazon SES supports two methods of authentication: Sender Policy Framework (SPF)
and DomainKeys Identified Mail (DKIM). For more information, see
Authenticating Your Email in Amazon SES.
If an ISP detects sudden, unexpected spikes in the volume or rate of your
emails, the ISP might suspect you are a spammer and block your emails. Therefore,
every Amazon SES account has a set of sending limits to regulate the number of
email messages that you can send and the rate at which you can send them.
These sending limits help you to gradually ramp up your sending activity
to protect your trustworthiness with ISPs.
Amazon SES has two sending limits: a sending quota (the maximum number
of messages you can send in a 24-hour period) and a maximum send rate
(the maximum number of emails that Amazon SES can accept from your account
per second, although the actual rate at which Amazon SES accepts
your messages might be less than the maximum send rate). If you are a
brand-new user, Amazon SES lets you send a small amount of email each day.
If the mail that you send is acceptable to ISPs, this limit will gradually increase.
Over time, your sending limits will steadily increase so that you can send
larger quantities of email at faster rates. You can also file an
SES Sending Limits Increase case to get your quotas increased if you need them
to ramp up more quickly.
For more information about sending limits and how to increase them,
see
Managing Your Amazon SES Sending Limits.
Many ISPs use content filtering to determine if incoming emails are spam.
Content filters look for questionable content and block the email if the email
fits the profile of spam. Amazon SES uses content filters also.
When your application sends a request to Amazon SES, Amazon SES
assembles an email message on your behalf and then scans the message header
and body to determine if they contain content that ISPs might construe as spam.
If your messages look like spam to the content filters that Amazon SES uses,
your reputation with Amazon SES will be negatively affected. If a message
is infected with a virus, it is rejected by Amazon SES entirely.
When it comes to email sending,
reputation—a measure
of confidence that an IP address, email address, or sending domain is not the source
of spam—is important. Amazon SES maintains a strong reputation with ISPs
so that ISPs deliver your emails to your recipients' inboxes. Similarly, you need
to maintain a trusted reputation with Amazon SES. You build your reputation with
Amazon SES by sending high-quality content. When you send high-quality content,
your reputation becomes more trusted over time and Amazon SES increases your
sending limits. Excessive bounces and complaints negatively impact
your reputation and can cause Amazon SES to lower your sending limits or
terminate your Amazon SES account.
One way to help maintain your reputation is to use the mailbox simulator
when you test your system, instead of sending to email addresses that you
have created yourself. Emails to the mailbox simulator do not count toward
your bounce and complaint metrics. For more information about the mailbox
simulator, see
Testing Amazon SES Email Sending.
High-quality email is email that recipients find valuable and want to receive.
Value means different things to different recipients and can come in the form of
offers, order confirmations, receipts, newsletters, etc. Ultimately, your deliverability
rests on the quality of the emails that you send because ISPs block emails that they
find to be low quality (spam). For more information about how to send high-quality email,
see
Improving Deliverability with Amazon SES
and the
Amazon Simple Email Service Email Sending Best Practices whitepaper.
Whether your deliveries fail, your recipients complain about your emails, or Amazon SES
successfully delivers an email to a recipient's mail server, Amazon SES helps you to track
down the issue by providing notifications and by enabling you to easily monitor your usage
statistics.
When an email bounces, the ISP notifies Amazon SES, and Amazon SES notifies you.
Amazon SES notifies you of hard bounces and soft bounces that Amazon SES will no
longer retry. Many ISPs also forward complaints, and Amazon SES sets up complaint
feedback loops with the major ISPs so you don't have to. Amazon SES can notify you of
bounces, complaints, and successful deliveries in two ways: you can set your account
up to receive notifications through Amazon SNS, or you can receive notifications by email
(bounces and complaints only). For more information, see
Monitoring Using Amazon SES Notifications.
Amazon SES provides usage statistics so that you can view your failed
deliveries to determine and resolve the root causes. You can view your usage
statistics by using the Amazon SES console or by calling the Amazon SES API.
You can view how many deliveries, bounces, complaints, and virus-infected rejected
emails you have, and you can also view your sending limits to ensure that you stay
within them.
Improve Your Email-Sending Program
If you are getting large numbers of bounces and complaints, it's time to reassess
your email-sending strategy. Remember that excessive bounces, complaints, and attempts
to send low-quality email constitute abuse and put your AWS account at risk of termination.
Ultimately, you need to be sure that you use Amazon SES to send high-quality
emails and to only send emails to recipients who want to receive them. For more information,
see
Improving Deliverability with Amazon SES and the
Amazon Simple Email Service Email Sending Best Practices whitepaper.
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