Understanding Bounced Emails in Outreach

Objective

The purpose of this article is to information to Outreach Users regarding bounced emails.  

Applies To

• Outreach Users
• Emails

Why Emails Bounce

There are two types of bounces and a few reasons why they would occur.

Hard bounces

Hard bounces (a 5.x.x error) happen when an email can’t be delivered. Generally, this can be caused by an invalid email address or an unexpected error during sending. If this occurs, review the following: 

• Confirm the mail recipient address is correct and valid. 
• Confirm the domain name is correct. 
• Confirm the email and domain are not included in a block list. 

Soft bounces

Soft bounces (a 4.x.x error) are recognized by the email server but are returned to the sender for a variety of reasons:

• Recipient Mailbox is full (over quota)
• Email message is too small
• Email message is too large
• Email message is image only
• Email message contains flagged verbiage such as order status, desperate, etc.
• Sending Domain has not been authenticated
  • You can authenticate your sending domain in the following ways:
    • SPF - Adds the IP addresses allowed to send email via your domain name in your DNS record
    • DKIM - Also based on the DNS record, this authentication solution is used to sign emails with a public or private key system
    • DMARC- This new technology allows the sender to check whether emails have been properly authenticated by the ISP or webmail

Note: Rarely, an email may not be recognized as a bounced email. This behavior is typical when the bounced email was routed to the wrong folder or the bounce itself was re-written to the extent where Outreach would not be able to parse through MIME content and determine the correct parent mailing.

Bounce Categories

To help you better understand why a message bounced, Outreach categorized a few common reasons into different categories outlined below. 

Flagged as Spam

Outreach Short Description: This message was flagged by spam by the recipient’s mailbox.

Every email that lands in your prospects inbox can be marked as spam. This message indicates that either your email was flagged by your customer’s IT team as spam because it did not meet their criteria to pass through to the designated mailbox, or your customer clicked on the “mark as spam” button when they saw your email in their inbox.

These emails should not be retried, since they will continue to bounce and potentially affect your email deliverability.

Note: Opt-out or remove Prospects with invalid email addresses to avoid future bounces.

Invalid Email

Outreach Short Description: The recipient email address does not exist.

The bounce message tells us that the email address was either entered incorrectly or is no longer an active mailbox (e.g., the prospect has left the company). This error is specific to the local part and/or email domain. The local part is the text found on the left of the @ symbol (rsiegel@), and the domain is the text found on the right of the at symbol(@outreach.io). If you believe this bounce message was received in error, make sure that the domain is spelled correctly and has the right domain end (.io, .com, .org, .edu, etc.). If the domain is correct, make sure the local part is correct (rachael.siegel@ vs resiegel@ vs rsiegel@). If the bounce error persists, then it is likely that the prospect has left the company and their emails are not being forwarded to another individual, such as a colleague or their manager.

It is possible, though unlikely, that the prospect’s email account has been suspended and is temporarily unable to accept emails.

Mailbox Full

Outreach Short Description: The recipient’s mailbox is full and cannot accept accept messages.

Some organizations set a limit on the number of emails an individual can have in their inbox at one time. Once the individual clears out old messages from their inbox, either by moving them into different folders or deleting them entirely, they’ll be able to receive new email.  This is a temporary error, so emails that receive this bounce category can be safely retried.

If you continue to receive this error after attempting to redeliver, it’s likely the email address is no longer in use.

Rejected by Recipients Mailbox

Outreach Short Description: This message was rejected by the recipient's mailbox due to a policy violation or security error.

Bounce messages that are rejected with this error are rejected due to the administrative settings the prospect’s company’s IT team has enabled as protection against unvetted senders.

Rejected due to Message Size

Outreach Short Description: This message exceeded the maximum size the recipient's mailbox accepts.

This bounce message is letting you know that your email was not delivered to your prospect because it is too big. Size limits are set by the prospect’s company’s IT team, who do not provide visibility into what, specifically, is causing the email size to exceed the limit. This is often a combination of email elements, including the amount of text, attachments, and embedded images.

Alternatively, it’s possible that a single element, such as an attachment, is too large. Outreach recommends a combined email size of no more than 5MB, including images and attachments. We’d also suggest compressing images into smaller files. A balance of text with images and attachments are best practice for email deliverability.

Unable to Connect to Recipient Mailbox

Outreach Short Description: Message delivery was delayed by recipient's mailbox. Try again.

In some cases, bounces are caused due to an error from the prospect’s server. Unlike other bounce reasons, these are usually temporary errors and the bounced email can be retried for successful delivery.

Unable to Determine Bounce Reason

Outreach Short Description: Not enough information to determine bounce reason.

Bounce reasons are provided by your prospect’s company’s mailbox policies, which are set by IT Administrators. In most instances, some information is provided within the bounce message, which is where the bounce reason is provided. Bounce reasons are optional, so not every company will provide detail into why your message could not be delivered. If you received this bounce category, we either do not have enough detailed information about the email bounce to determine the cause, or the bounce reason is not in English.

Bounce due to 24 Hour Block

The 24-hour email block period will be triggered when sending bulk emails or sequencing on mass and the following thresholds are met. The thresholds are listed below.

1. The maximum amount of bounces for a user per the last 24 hours. Default value - 125
2. The maximum percentage of bounce emails vs all emails in the last 24 hours. Default value - 5%
   

Both conditions need to be met i.e. users need to have over 125 sends and 5% need to have bounced. There is a warning email triggered to users at 50% and 70% of the 5% limit being met.

What can I do to prevent bounces? 

The advice we typically give is to use a service to verify the emails you are trying to send to. Email Hunter and Rapportive are free and work fairly well. DiscoverOrg and Datanyze are not free, but they are very effective. Kickbox.io is another good resource for verifying large lists.

We also advise that you target a much smaller audience at companies instead of targeting everybody with an email address. For instance, our sales team is only allowed to contact 5 people at a company at any given time. Basically, if you are sending the same 100 emails to the same companies servers in a day, there is a high chance that server will block you. Bulk email by definition is spam, so If you are sending a similar copy to a lot of recipients at the same company, their mailing servers are more likely to pick up on it.

Outreach has a few ways that we can help. We have domain level throttling, which allows you to set the max number of emails one domain can be sent per 24 hours. We also have sequence throttling, which a lot of people overlook, but this is something that can not only help your workflow but also improve deliverability over the long run. Another thing here might be to limit the number of exact date and time sequences your users are running. The intervals of an interval sequence would help email deliverability as your emails would be spread out over a defined schedule of time, and not all delivered at the same time to your prospects. Lastly, as a final safety measure, if a large number of emails all bounce during a short time period, Outreach will temporarily lock your mailbox for 24 hours. This is to help ensure that your email domain's reputation score is protected, as bounced emails can damage the reputation for your entire organization and mean that all of your emails are more likely to be flagged as Spam.

As far as domain monitoring, we recommend MXtoolbox. They can provide comprehensive blacklist checks and domain health reports.

Additional Resources

Review the below to ensure that all of the hard work you put into writing emails lands in the inboxes of your prospects.

• Outreach Email Best Practices: Avoiding Spam Filters
• The Outreach Email Deliverability Playbook