Email best practices

Even when you have your customers' best interests in mind, you might still encounter situations that impact the deliverability of your messages. The following sections contain recommendations to help make sure that your email communications reach your intended audience.

General recommendations

• Put yourself in your customer's shoes. Ask yourself if the message that you're sending is something that you would want to receive in your own inbox. If the answer is anything less than an enthusiastic "yes!" then you probably shouldn't send it.

• Some industries have a reputation for poor quality or even malicious email practices. If you're involved in the following industries, you must monitor your reputation very closely and resolve issues immediately:

  • Home mortgage

  • Credit

  • Pharmaceuticals and supplements

  • Alcohol and tobacco

  • Adult entertainment

  • Casinos and gambling

  • Work-from-home programs

Domain and "from" address considerations

• Carefully consider the addresses that you send email from. The From address is one of the first pieces of information your recipients see, and therefore can leave a lasting first impression. Additionally, some ISPs associate your reputation with your From address.

• Consider using subdomains for different types of communications. For example, assume you're sending email from the domain example.com, and you plan to send both marketing and transactional messages. Rather than sending all of your messages from example.com, send your marketing messages from a subdomain such as marketing.example.com, and your transactional messages from a subdomain such as orders.example.com. Unique subdomains develop their own reputations. Using subdomains reduces the risk of damage to your reputation if, for example, your marketing communications land in a spam trap or trigger a content filter.

• If you plan to send a large number of messages, don't send those messages from an ISP-based address such as [e-mail]. If an ISP notices a large volume of messages coming from [e-mail], that email is treated differently than an email that comes from an outbound email sending domain that you own.

• Work with your domain registrar to make sure that the WHOIS information for your domain is accurate. Maintaining an honest and up-to-date WHOIS record demonstrates that you value transparency, and allows users to quickly identify whether your domain is legitimate.

• Avoid using a no-reply address, such as [e-mail], as your From or Reply-to address. Using a no-reply@ email address sends your recipients a clear message: that you aren't offering them a way to contact you, and that you're not interested in their feedback.

Building and maintaining your lists

• Implement a double opt-in strategy. When users sign up to receive email from you, send them a message with a confirmation link, and don't start sending them email until they confirm their address by selecting that link. A double opt-in strategy helps reduce the number of hard bounces resulting from typographical errors.

• When collecting email addresses with a web-based form, perform minimal validation on those addresses upon submission. For example, make sure that the addresses you collect are well-formed (that is, they are in the format [e-mail]), and that they refer to domains with valid MX records.

• Use caution when allowing user-defined input to be passed to Amazon Pinpoint unchecked. Forums registrations and form submissions present unique risks because the content is completely user-generated, and spammers can fill out forms with their own content. It's your responsibility to make sure that you only send email with high-quality content.

• It's highly unlikely that a standard alias (such as postmaster@, abuse@, or noc@) will ever sign up for your email intentionally. Make sure that you only send messages to real people who actually want to receive them. This rule is especially true for standard aliases, which are customarily reserved for email watchdogs.

Compliance

• Be aware of the email marketing and anti-spam laws and regulations in the countries and regions that you send email to. You're responsible for making sure that the email you send complies with these laws. This guide doesn't cover these laws, so it's important that you research them. For a list of laws, see Email spam legislation by country on Wikipedia.

• Always consult an attorney to obtain legal advice.

Sending a high volume of email

Consistency is important when sending email. When increasing email volume, it's important to steadily increase sending volume each day, with similar types of messages being sent at around the same time every day. However, situations might arise that require you to send an especially large volume of email to your customers. An example might be a Terms of Service update. There are several steps that you can take to protect your sender reputation and achieve high deliverability rates when increasing volume.

• Organize your recipient list to create segments of those customers who are most likely to open your email, and those who are most likely to mark your message as spam or unsubscribe.

  Build a foundation of trust with email providers by sending messages to the most engaged portion of the segment first.

• Spread out your campaign over several hours throughout the day, rather than sending all of your messages at once.

  Mimic your normal sending cadence when possible. For example, if on a normal day you send your list of 1M an email but split them into two distributions, one beginning at 8 AM and one at Noon, but if you needed to send 5M out one day, send in splits like your normal sending day.

• When you send volumes of email that are larger than your normal volumes, try to send in multiples of your typical volume.

  For example, if you send 250,000 emails on a normal day, try to limit higher-volume events to a multiple of that amount, such as 500,000 or 750,000. Limiting your sending volume in this way demonstrates to email providers that although you’re sending more email than normal, you’re still carefully maintaining your volume.

Bounces

A bounce occurs when an email can't be delivered to the intended recipient. There are two types of bounces: hard bounces and soft bounces. A hard bounce occurs when the email can't be delivered because of a persistent issue, such as when an email address doesn't exist. A soft bounce occurs when a temporary issue prevents the delivery of an email. Soft bounces can occur when a recipient's inbox is full, or when the receiving server is temporarily unavailable. Amazon Pinpoint handles soft bounces by attempting to re-deliver soft bounced emails for a certain period of time.

It's essential that you monitor the number of hard bounces in your email program, and that you remove hard-bouncing email addresses from your recipient lists. When email receivers detect a high rate of hard bounces, they assume that you don't know your recipients well. As a result, a high hard bounce rate can negatively impact the deliverability of your email messages.

The following guidelines can help you avoid bounces and improve your sender reputation:

• Try to keep your hard bounce rate below 5%. The fewer hard bounces in your email program, the more likely ISPs will see your messages as legitimate and valuable. This rate should be considered a reasonable and attainable goal, but isn't a universal rule across all ISPs.

• Never rent or buy email lists. These lists can contain large numbers of invalid addresses, which could cause your hard bounce rates to increase dramatically. Furthermore, these lists could contain spam traps—email addresses specifically used to catch illegitimate senders. If your messages land in a spam trap, your delivery rates and sender reputation could be irrevocably damaged.

• Keep your list up to date. If you haven't emailed your recipients in a long time, try to validate your customers' statuses through some other means (such as website login activity or purchase history).

• If you don't have a method of verifying your customers' statuses, consider sending a win-back email. A typical win-back email mentions that you haven't heard from the customer in a while, and encourages the customer to confirm that they still want to receive your email. After sending a win-back email, purge all of the recipients who didn't respond from your lists.

When you receive bounces, it's important that you immediately remove that address from your lists. Don't attempt to re-send messages to hard-bouncing addresses. Repeated hard bounces can ultimately harm your reputation with the recipient's ISP.

If you receive a hard bounce, you should note the following:

• The recipient's email address is added to a global suppression list for a period of 14 days. When you send an email and the recipient's address is on the global suppression list, the message is still accepted. However, Amazon Pinpoint doesn't attempt to deliver the message to the recipient.

• When an email hard bounces, it's important to remove the recipient's email address from your mailing lists. When you send email to an address that's on the global suppression list, Amazon Pinpoint generates bounce events, even though the email isn't sent. These bounce events count against your account's bounce rate. If your bounce rate gets too high, we might place your account under review in order to protect your reputation as a sender.

For more information about the global suppression list, see Amazon SES global suppression list.

Complaints

A complaint occurs when an email recipient selects the "Mark as Spam" (or equivalent) button in their web-based email client. If you accumulate a large number of these complaints, the ISP assumes that you're sending spam. This has a negative impact on your deliverability rate and sender reputation. Some, but not all, ISPs will notify you when a complaint is reported, which is known as a feedback loop. Amazon Pinpoint automatically forwards complaints from ISPs that offer feedback loops to you.

The following guidelines can help you avoid complaints and improve your sender reputation:

• Try to keep your complaint rate below 0.1%. The fewer complaints in your email program, the more likely ISPs will see your messages as legitimate and valuable. This rate should be considered a reasonable and attainable goal, but isn't a universal rule across all ISPs.

• If a customer complains about a marketing email, you should immediately stop sending that customer marketing emails. However, if your email program also includes other types of emails (such as notification or transactional emails), it might be acceptable to continue to send those types of messages to the recipient who issued the complaint.

• As with hard bounces, if you have a list that you haven't sent email to in a while, make sure that your recipients understand why they're receiving your messages. We recommend that you send a welcome message reminding them of who you are and why you're contacting them.

When you receive complaints, it's vital that you respond to them appropriately by observing the following rules:

• Make sure that the address you use to receive complaint notifications is able to receive email.

• Make sure that your complaint notifications aren't being marked as spam by your ISP or mail system.

• Complaint notifications usually contain the body of the email. This is different from bounce notifications, which only include the email headers. However, in complaint notifications, the email address of the individual who issued the complaint is removed. Use custom X-headers or special identifiers embedded in the email body so that you can identify the email address that issued the complaint. This technique makes it easier to identify addresses that complained so that you can remove them from your recipient lists.

Message quality

Email receivers use content filters to detect certain characteristics of messages and determine whether a message is legitimate. These content filters automatically review the content of messages to identify common traits of unwanted to malicious messages. Amazon Pinpoint uses content filtering technologies to help detect and block messages that contain malware before they are sent.

If an email receiver's content filters determine that your message has characteristics of spam or malicious email, your message will most likely be flagged and diverted from recipients' inboxes.

Remember the following when designing your email:

• Modern content filters are intelligent, continuously adapting and changing. They don't rely on a predefined set of rules. Third-party services such as ReturnPath or Litmus can help identify content in your email that might trigger content filters.

• If your email contains links, check the URLs for those links against denylists, such as those found at URIBL.com and SURBL.org.

• Avoid using link shorteners. Malicious senders might use link shorteners to hide the actual destination of a link. When ISPs notice that link shortening services—even the most reputable ones—are being used for nefarious purposes, they might denylist those services altogether. If your email contains a link to a denylisted link shortening service, it won't reach your customers' inboxes, and the success of your email campaign suffers.

• Test every link in your email to verify that it points to the intended page.

• Make sure that your website includes Privacy Policy and Terms of Use documents, and that these documents are up to date. It's a good practice to link to these documents from each email you send. Providing links to these documents demonstrates that you have nothing to hide from your customers, which can help build a relationship of trust.

• If you plan to send high-frequency content (such as "daily deals" messages), make sure that the content of your email is different with each deployment. When you send messages with high frequency, you must make sure that those messages are timely and relevant, rather than repetitive and annoying.