Email non-delivery and complaints

Non-deliveries and complaints are a means of communicating issues for a particular recipient’s experience.

Because of this, they should be treated with the sincerity of what they represent to help protect your recipients' experience with your emails, as well as to help identify issues with your sending practices should an unexpected trend of bounces or complaints occur.

Avoiding email non-delivery and complaints is helpful for maintaining strong email deliverability, as too much of these can have a negative consequence on your sender reputation. Employing deliverability best practices will help you to do so and more easily land your email messages in your audience’s inboxes.

Learn more about email deliverability and crafting email messages to protect deliverability under Improving email deliverability.

Email non-delivery activities

Email non-delivery can be the result of issues with the email content (an Invalid email activity) or with something on the recipient’s side (Bounced email and Deferred email activities). A complaint means that the recipient has marked your email as spam (Abuse reported). You can view email non-delivery activity under Activities and in Reports.

Invalid emails are tracked separately and are not counted within the Sent email activity. This is because the Invalid email activity occurs before an email is sent. However, bounced and deferred emails are counted within Sent email, while also being tracked as separate activities.

Bounced email (hard and soft bounces)

An email bounces when its delivery was rejected by the recipient’s mail server. The reason an email is rejected for delivery determines if that bounce is considered hard or soft.

hard bounce means the email has been permanently rejected because the email address is invalid or doesn’t exist. For instance, a spelling error in a person’s (contact’s) email address may cause a hard bounce. Or an unused mailbox was suddenly shut down by the mailbox provider because of disuse.

A person’s email address is unsubscribed automatically after they have hard-bounced once and a subsequent send is attempted (if the first send hard-bounces, the second send unsubscribes the person and will not attempt delivery). We do this to ensure that your sender reputation remains high. Continuing to try to send to someone with a known bad address will harm your sender reputation, which affects how likely your email is to end up in someone’s inbox.

soft bounce means that the email address was more than likely valid and the email reached the recipient’s mail server. However, it bounced back because of a temporary issue, like an outage on their end, or a block.

Blocks are treated as soft bounces because they are less permanent than a hard bounce. A block may be the result of your internet protocol (IP) address or domain being added to a blacklist, or a technical issue between the mail servers.

Most bounces experienced within your Ortto account are not due to an IP block, thanks to the protective sending limitations around our acceptable usage policy and the active work of our internal Deliverability team. However, if you notice a trend in bounces that you need help investigating or appear to be due to some sort of block, please reach out to our Support team by emailing

Manually resubscribe a person

You can manually resubscribe people if needed, for example to fix an email address spelling error that caused an initial hard bounce. This should generally only be done in the case where you had an incorrect email address for a contact and have corrected it.

CAUTION: Use caution when doing this, as continually emailing people who have previously hard-bounced will affect your sender reputation.

Learn more about editing a person’s subscription preferences under Viewing and editing a person.

Invalid email

An Invalid email activity is triggered before the email is sent. Reasons for an invalid email include:

  • the content of the email was empty
  • a permanent delivery issue occurred with a previous attempt to this subscriber
  • various unsubscribe activities
  • the subscriber's email value was empty (e.g. you used a merge tag with no default value).

NOTE: Invalid email activity doesn’t have a retention limit and is tracked for the life of your Ortto account.

Invalid email statuses

The following table describes the Email status attributes for an Invalid email activity.

drop (dropped) refers to the email being dropped when sent from Ortto, before actually connecting with the mail server (we don’t receive bounces for these). Drops occur in an effort to protect your sender reputation, so that mail servers to not record your sends as hard bounced or spam reported email addresses.

Ortto’s email sending function is supported by SendGrid, which has it’s own suppression list to protect both Ortto’s and your (the sender) sender reputation.

NOTE: Most of these statuses will result in a contact’s email address being automatically suppressed. So if you are using a suppression filter for invalid email statuses, it is generally not necessary.

Invalid email status


Contact was unsubscribed

Contact was unsubscribed and attempted to be sent to.

Dropped: Bounced address

The address hard bounced at least once and is now on a bounced suppression list handled by SendGrid.

Dropped: Invalid

Likely typo or non-existent domain addresses for major providers. For example,

Some of these types of domain misspellings have been connected with spam traps (email addresses designed to look like real email addresses, created by spammers), and so are dropped as a safety measure.

Dropped: Spam reported address

The recipient has previously reported one of your emails as spam and their address is now on a suppression list handled by SendGrid.


Is related to repeated attempts at triggering the same send (i.e. an address that has already been sent a particular campaign). Can be related to the same contact record repeatedly triggering an automation such as a journey that’s already been successfully triggered and delivered or due to multiple contact records with the same email address.

Email prevention limit reached

The email limit set in your account has been reached so the recipient was not sent a particular email (also captured as the Skipped email activity).


By default a non-functioning email address format. For example, hello where there is a space in the email address causing the problem.


It is usually related to a one-time experience and doesn’t cause issues for future campaign attempts to that address. This may be related to an error with the API that handles email sends.

If you are using a suppression filter for Invalid email, we don’t recommend adding Temp-error email addresses, as these are likely ok to use.

Missing from email

The "from" email was missing at the time the email was sent. This might happen if you use a merge tag to populate the From email address field and the email value is invalid, for example.


The email was missing a subject line at the time the email was sent, and was rejected by SendGrid.

Missing JSON document

The email was configured to use dynamic content at a "per contact" request level and the contact's ID was missing from the JSON endpoint. As a result, the email was not sent to that contact.

IMPORTANT: For email addresses where you believe the invalid status is due to a typing error (e.g. instead of, you should not attempt to edit it in the person’s CDP profile (view) without that person’s permission. Permission to send communications has been granted only for the provided email address.

Regardless of whether a person has intentionally or unintentionally provided a misspelled email address, if you edit it and start sending communications to the "correct" address:

  • You will be sending communications to a person who has not consented to receive communications at that address (e.g. permission was granted for not
  • You might incorrectly edit the email address, resulting in emails sent to a completely different person than the intended recipient (e.g. was changed to, but was the correct address).

Sending emails to recipients who have not consented can result in the recipient reporting your emails as spam which can harm your sender reputation.

To correct what you think might be an email address typing error, you should attempt to collect the "correct" email address through the normal channels available. For example, reach out to the person and ask if they are happy for you to edit the email address in their profile, or ask if they want to (re)submit their email address (and consent to receive communications) via a form on your website.

You can try to prevent misspelled email addresses by adding a "Confirm email address" field on forms that capture email permissions, so a person can check they are correctly typing their email address.

Deferred email

Sometimes, an attempt to deliver email results in a deferral from the recipient’s mail server. This means that the recipient’s mail server has temporarily refused delivery of an email.

If this occurs, Ortto will attempt to send the email for up to 72 hours until it is delivered (resulting in a Sent email activity). If the email still cannot be delivered over the 72-hour period, it will be considered bounced (resulting in a Bounced email activity).


Complaints are an important part of the email ecosystem, as they allow recipients to advise that the email received was perceived as spam (possibly malicious, unsolicited, undesired, and/or irrelevant).

Complaints are very harmful to a sender’s reputation, when multiple occur.

The industry-acceptable level of complaints for a permission-based sender is below 0.02% or less than 2 out of every 10,000 subscribers.

IMPORTANT: If a person marks your email as spam (Abuse reported activity), that person will automatically be unsubscribed from all email.

Should you see a string of complaints that go above the advised threshold, stop sending and check your audience subscription preferences. This experience means that subscribers believe that you are sending mail that they did not ask for, and it only takes a smaller number of these complaints to see a drop in sender reputation.