# Email settings > You can go to the Settings tab to apply global settings for all emails. Source: https://help.kustomer.com/en_us/email-settings-Hk7yYirdC Last updated: 2026-08-05T21:59:27.068Z To manage your organization's email addresses and domains, visit your Email channel and click the **Settings** tab**.** The settings page will contain all configurations for both Amazon SES and Postmark settings (for those who have not [completed migration to Amazon SES](https://help.kustomer.com/en_us/enabling-the-amazon-ses-email-channel-in-kustomer-B1fw0fJGMl#starting-the-migration)).  From the **Settings** tab, specify how emails are threaded, review your existing spam rate, or change your inbound spam threshold. **Global email settings** * **Disable Email Preview** Turn on to hide the View Full Email option. Users will not be able to open the email in a separate window. * **Filter Email Content in Preview** Turn on to hide unsafe content from emails, such as images. * **Block outbound file extensions (beta access)** Turn on to block agents from attaching the selected files to an email. You can block the following file extensions: **File type** aac gz mpeg rar wma amr m4a mpg rm wmv avi m4v ogg swf xls doc mkv opus tar xlsx docx mov pdf vob zip flac mp3 ppt wav 7z flv mp4 pptx webm **Add threading to email** You can choose how your organization threads replies and the email conversation history style that best suits your business's needs. By default, replies to emails only include the contents of that reply. However, you can also include the history of the previous conversation in your replies if you prefer. **Note:** This setting only applies to email addresses for custom or Kustomer domains. If you have a connected Gmail address, you can [specify threading](https://help.kustomer.com/en_us/gmail-setup-BJj0xnL4#email-threading) for it in Gmail settings. The following options are available in the Add threading to email section: * **Single message replies** will send only the current reply when responding to an email. * This may be useful if your customers usually contact you multiple times in succession, but tend to have different and unrelated questions each time they reply. * Or, if you exchange many messages with users while resolving their concerns, and the full history is not important to newer messages. * **Include history in replies** will include all previous emails in the current conversation thread.  * For example, a customer would see their earlier message and remember their initial question about when a package would arrive, avoiding confusion when you send the tracking link. * This also might be useful in troubleshooting contexts where your team has to work back and forth to collect information from a customer. **Review your spam complaint rate** Your spam rate is an indicator of how frequently recipients are marking your emails as spam. To avoid issues with your outgoing emails, your spam rate should be less than 0.10%, or 10 complaints for every 10,000 sent emails.  **Note:** This setting only applies to email addresses for custom or Kustomer domains. ![](https://cdn.kustomerhostedcontent.com/media/570fad9d9001bc1000163b28/84444b088537153c9a4fe7acbe1d548b.png) The following colors will indicate your current rate. **Spam rate** **Color** Greater than 0.1% Red Below 0.1% Green Equal to 0.1% Yellow **Filtering inbound spam** To control spam, Amazon SES uses a series of steps designed to scan inbound email for spam and malware. When you set a spam threshold, Amazon SES will block all emails that have a score that is lower than that threshold. The lower the threshold, the more restrictive it is and fewer emails that are suspected to be spam will reach your inbox. For example, if you set your threshold to 5, only emails with a spam score of 1-4 will go through. The spam threshold can be set anywhere from 1-30. We recommend you set your threshold to 5 and adjust it, as needed. You can view all emails marked as spam by going to your Spam search. If you notice that many spam emails are reaching your inbox, you may want to increase the threshold.  **Notes:**  * You can turn this setting off using the toggle. Once off, all inbound emails will be allowed to go through, regardless of its spam score. * This setting only applies to email addresses for custom or Kustomer domains. For more information see [this article from Amazon SES](https://docs.aws.amazon.com/ses/latest/dg/receiving-email-concepts.html). #### **Block list and auto-reply business rules** Adding an email address to the block list marks incoming messages from that address as spam and can auto-close the conversation. However, business rules that trigger on conversation creation or message receipt may still fire before the spam classification takes effect. If you have an auto-reply business rule (such as an email deflection rule), add a condition to exclude blocked email addresses from triggering the auto-response. For example, add a condition where the sender email **does not contain** the blocked address. This prevents automated replies from being sent to transactional or no-reply email addresses that should not receive responses. #### **Block file attachment types in outbound email** You can prevent agents from attaching specific file types (such as zip or exe) to outbound emails. This helps enforce compliance and security policies. To block outbound file attachment types: 1. From the left navigation, click **Settings**. The Settings page opens. 2. In the **Settings** page, click **Apps**, then select **Email**. 3. Click the **Settings** tab. 4. In the __Block outbound file extensions__ field, enter the file extensions you want to block (for example, zip and exe) 5. Click **Save**. **Note:** This setting applies to outbound emails only. Kustomer does not support blocking inbound file attachments from customers on any channel. ### **Outbound email address selection** When an agent composes or replies to an email, the outbound "From" address defaults to the first address listed on the **Your Support Addresses** settings page. To change the default: 1. From the left navigation, click **Settings**. The Settings page opens. 2. In the **Settings** page, click **Channels & Apps**, then select **Email**. 3. On the **Your Support Addresses** page, drag and reorder the email addresses. The first address in the list appears as the default in the compose area. Agents can manually select a different outbound address from the dropdown in the compose area before sending. **Note:** Per-team or per-queue default outbound email addresses are not currently supported. All agents see the same default address regardless of team assignment. To request this feature, submit feedback through the Kustomer product feedback process. **Note:** Kustomer sends all outgoing emails as `multipart/alternative`. This means every email contains both a plain text and an HTML MIME part, regardless of the email template used. ### **How outgoing email format works** When an agent sends an email from Kustomer, the platform automatically generates both a plain text and an HTML version of the message. The recipient's email client determines which version to display. This behavior occurs at the infrastructure level. It cannot be modified through template configuration, the `{{draft.textBody}}` variable, or the API. ### **Known limitation with plain-text-only delivery** Some external systems flag or reject emails that contain an HTML MIME part, even if the visible content is plain text. Because Kustomer always includes the HTML MIME part, there is no current workaround to send plain-text-only emails. If your recipients require plain-text-only email delivery, contact Kustomer Support to submit a feature request. ### Related articles: * [Receive email in Kustomer](https://help.kustomer.com/en_us/receive-email-in-kustomer-rJWnIhva) * [Connect your Gmail address to Kustomer](https://help.kustomer.com/en_us/gmail-setup-BJj0xnL4)