Email Deliverability and Spam Control

Email deliverability is important for any organization and ensuring that you receive your customers’ emails and your customers receive the responses you want to send them is vital.  Kustomer sends and receives email through one of two methods: Postmark or Gmail.  We typically recommend Postmark, as this allows for some more control over issues that may come up with both your inbound and outbound emails. In this blog post, we will review some of the issues you may encounter and how to handle them effectively to make sure you and your customers can successfully communicate with each other over email.


Outbound Deliverability


When you send an email out through Kustomer, you may choose to send using the default email address setup for your user account or use any of the other email addresses you have already setup within Kustomer.  It is important to setup and use only email addresses that are used as transactional addresses and not used for marketing to decrease the chances your email is treated as spam.  

Still, there are times when upset customers or overzealous spam filters can flag your transactional messages as spam.  Some inboxes will do this quietly and just hide the messages in a user’s spam folder, and others will send back a spam complaint notice to the email server that sent the message.  This will result in an error message on the customer timeline as well as a note added to Kustomer’s Org Logging section that can be monitored by administrators.   The overall spam rate and rating for your account’s email server (specific to you) is calculated on a running 30-day basis. If you are using Postmark this rating will be displayed under Apps > Channels > Email for users with access to this section. 



When an email is successfully received by the recipient’s email server, Kustomer will display the timestamp below the message in the timeline, which will let you know the email was accepted by the email server on the other end.  Any issues with the deliverability will result in a red error notification that you can hover over to see more details.  Apart from spam complaints, other errors you may encounter when sending customers emails are: Soft Bounces, Hard Bounces, and ISP Blocks. 



Soft bounces are generally issues of full inboxes and can occur if the inbox has a message quota or overall size limitation.  If you encounter this type of error, it is best to either try reaching the person through another contact method or waiting to try sending the email again once they have had some time to clear up space in their inbox.


ISP Blocks result from email administrators establishing certain rules that prevent emails from getting through and oftentimes come from schools, governments, or corporations that want to restrict what types of email addresses can communicate with the email addresses they manage.  Like with soft bounces, it is generally a good idea to look for other channels to contact your customer on, as this is a blockage beyond our control, and one your customer is likely unaware of.



Hard bounces can result from typos in the address, network issues with the recipient email server, or an email address that no longer exists or has been deactivated.  In the event of a hard bounce error, double check that the spelling of the address is correct.  A hard bounce results in Postmark deactivating the address from eligible sending going forward, but if the address was only temporarily deactivated or there were network issues with the receiving email server, it may be possible to reactivate the address and still deliver your message.  If you believe the address is typed correctly and should be working, please contact Kustomer support to see if there are potential remedies to the situation.


Inbound Spam Control


Now that you are successfully sending emails to your customers, let’s talk about how to handle the emails your organization receives.  If you are using Postmark, then you are likely receiving your inbound emails to a separate inbox (like Gmail) that is auto-forwarding these messages into the Kustomer-provided Postmark email address.  Because only the inbox is auto-forwarded into Kustomer, we do not have visibility into the spam folders or filters that may exist on that end.  So, if you are using Gmail, it is good practice to check the spam folder there periodically and confirm none of your customer emails are getting stuck there.  With other inboxes that allow control over the spam threshold, we recommend having this open and forgiving so that you can use controls within Kustomer to have greater visibility and control over what messages are making their way into the platform.  When a conversation is flagged in Kustomer as spam, a business rule will automatically mark the conversation as Done and add a Spam: true attribute on the conversation so that it can be removed from your reporting.


Messages are scanned on their way into Kustomer and assigned a spam score based on the message content and the sending domain’s reputation.  Within Kustomer, we can manage which messages get flagged as incoming spam based on this score, and you are able to adjust this under Apps > Channels > Email.  We recommend setting the threshold to 5 and adjusting the value, as needed (All emails marked as spam can be found later with a Search in Kustomer).  If your organization does not want to filter suspected spam messages, set the threshold to 0 to turn it off. 


Apart from the automatic spam filtration, users have a couple of manual options available to them.  You can manually flag conversations as spam using the 3-dots to open up the conversation menu:


Marking a conversation as spam will automatically mark it Done as well as add the sender address to a block list that will prevent their messages from getting through again.  You can also manually add specific email addresses or entire domains to this block list by going to Settings > Administration > Spam Filters. 


With these tools in hand, you and your organization are able to decrease the noise caused by unwanted spam messages and focus on what matters most: your customers. 

If you run into any issues or have any questions regarding anything in this post, please reach out to

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