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Optimizing email deliverability
Optimizing email deliverability

This article outlines best practices for protecting your email reputation and preventing your emails from getting marked as spam.

Updated over a week ago

Emails can easily get lost in spam folders. So, it's critical to ensure that your message stands out and bypasses spam filters.

Spam filtering is a complex topic. Many mail services use various technologies to detect and filter spam and data from several sources to inform their filtering. Because of this, Mixmax, like any other service, cannot guarantee that your messages will not be filtered. But there are steps you can take to maximize the chance that your messages are received and opened, and Mixmax will help you reach that goal!

Google email sender guidelines

Starting February 2024, Gmail requires that senders who send 5,000 or more messages a day to Gmail accounts meet the requirements outlined in Gmail guidelines for email senders. Even if you send fewer emails a day but foresee that number increasing at some point, you should take certain proactive measures to ensure your emails are not flagged as spam.

Below are some best practices for protecting your email reputation that Mixmax recommends. You will also learn what settings you can configure in Mixmax and outside of it to optimize email deliverability and become compliant with Gmail regulations.

Settings for custom domains

If you use Google Workspace and have a custom email domain, you should ensure that standard email security settings are configured for your domain. You should also make sure you can get information about your domain's email reputation.

Outlined in the sections below, you will find the settings that are partially or entirely external to Mixmax. We strongly recommend getting them in place before sending Mixmax messages or sequences.


SPF, DKIM, and DMARC are tools for authenticating email messages. They ensure that email messages are sent from an authorized server and have a digital signature that validates the sending server. Having these in place ensures your recipients that your domain is sending these messages and will make anything you send significantly less likely to be filtered as spam.

You can check the Email Diagnostic page in the Mixmax dashboard to see if SPF, DKIM, and DMARC have already been configured for your domain. If they have not, you should work with your IT team, DNS administrator, or hosting provider to add the appropriate DNS records and Google Workspace settings.

Email diagnostic

SPF, DKIM, and DMARC are maintained by you or your hosting provider, not Mixmax, and cannot be modified through Mixmax. You will need help from your IT team to ensure these are configured correctly.

You can find additional information about these tools and how to set them up for your Google Workspace domain in the articles linked below:

SPF records specify which mail servers are permitted to send emails on behalf of your email domain. It prevents spammers from sending emails that pretend to be from your domain. If your SPF records are not set up correctly, your emails may not be accepted by your recipient's mail server (resulting in a bounceback email) or get caught in your recipient's spam filters.

DKIM is a digital signature that you can add to your outgoing mail. It encrypts your email header and enables email servers that receive your message to verify that it is coming from your email domain.

DMARC is a protocol that uses SPF and DKIM to determine whether an email message is authentic. Adding a DMARC record will improve the deliverability of your email.

Custom Domains in Mixmax

Mixmax allows you to use your custom domain for Mixmax open, link tracking, and Calendar links. Using a custom domain for tracking ensures that you send links that look like they come from you directly. It improves your deliverability in two ways:

  • Messages with links to the same domain as the sender help affirm your identity and are less likely to be filtered.

  • Messages with links to your domain will not appear similar to messages sent by other Mixmax users, which prevents your messages from being associated with other senders.

Setting up custom domains requires additional DNS entries to be configured in your domain, and you may need assistance from your IT team, DNS administrator, or hosting provider. See our article Custom Domains for Tracking and Calendars for the necessary steps.

Google Postmaster Tools

Google's Postmaster Tools allow you to see additional data about your domain's email traffic, reputation, and spam rates. We recommend configuring this service for your domain. If you send only a tiny amount of traffic, these statistics may not be available initially, but setting the service up will allow you to see once you have sent a sufficient volume of emails.

You should monitor these statistics and consider changing your outbound email strategy if you start to see negative changes. In particular, if you see a user-reported spam rate above 0.3%, you should change your email content. Users manually reporting spam at that rate will significantly affect your deliverability.

See Google's article Getting Started with Postmaster Tools to learn more about setting this up.

Microsoft 365 email authentication standards

Outlook-based users can improve email deliverability by following a set of Microsoft 365 standards, also known as email authentication or validation.

The email authentication protocols allow you not only to shield against phishing but also to ensure your emails land securely in recipients' inboxes, steering clear of spam filters.

To learn more about email authentication in Microsoft 365, see this Microsoft support article.

Settings for all users

These settings are internal to Mixmax and apply whether you have a email address or have your custom email domain.

Daily Send Limits

The Mixmax Daily Send Limit feature limits the sequence messages that users in your workspace can send daily. Recipients treat senders who send large amounts of email over short periods as more likely to be spammers. Limiting your daily sequence message volume will help to prevent this. Consider setting your Daily Send Limit to 300 or less, especially if your domain does not have a history of sending large amounts of emails. See our Daily Send Limit article for information on how to configure this.

Unsubscribe links

Unsubscribe links allow your recipients to tell you they don't want to hear from you anymore. Once they click the unsubscribe link, they will be automatically removed from any active Mixmax sequences and cannot be added to future sequences. Including an unsubscribe link is a best practice because it is polite to your recipients and because spam filters consider automated messages sent without unsubscribe links more likely to be spam.

You should configure your roles in Mixmax to have unsubscribe links in sequence messages. See our article Add an Unsubscribe link to your Sequences for details.

General Best Practices

We never recommend using Mixmax for blast marketing. By taking a more targeted approach and personalizing sequence emails, you can mitigate the risk of emails getting marked as spam and ensure your messages get delivered to the recipients successfully.

These are the additional steps you can take to improve your messages' deliverability:


  • Make sure your messages don't look automated. Use Mixmax Sequence variables to personalize messages and compose them like a hand-written letter. If your message reads like it was sent automatically, spam filters are more likely to treat it as spam.

  • Avoid terms and phrases that suggest your message is an attempt to sell a product, conduct a contest, or other explicitly commercial purposes. These messages are more likely to be filtered and manually marked as spam by recipients.

  • Use Mixmax AI Compose to fine-tune your existing email drafts and craft new personalized emails from prompts.

  • Conveniently access Salesforce or LinkedIn Sales Navigator data directly from your Gmail Inbox through the Mixmax Sidebar and utilize Mixmax Email Templates for a more efficient personalization workflow.


  • Keep your message-sending volume consistent. Sudden increases in message volume can be seen as a sign of spamming. If you need to increase your sending volume, ramp it up slowly.


  • Limit the use of HTML, images, and links. Large amounts of these in a message will trigger some filters.

  • Relatedly, consider disabling tracking if deliverability is your primary concern. Open, click, and download tracking rely on images or links in your message to function and can slightly increase the chance your message is filtered.

  • Include unsubscribe links in your sequences to ensure your recipients can opt out of further communication. Use Mixmax Rules and Salesforce integration to automatically update the Lead/Contact Opt-out status in your CRM.


  • Include Call, SMS, and LinkedIn tasks as your Mixmax sequence stages for multi-channel outreach. Avoid using only emails for prospecting.

  • Add manual email stages to Mixmax sequences to deliberately interrupt the chain of automated messages and provide more personal input.

  • If your sequence metrics start decreasing, you should change your sequence content. Mail systems treat messages with identical text to previous messages as more likely to be spam. Additionally, if recipients mark a message as spam, similar future messages will likely be filtered automatically. Changing your content can help to avoid this.


  • Send messages to known good email addresses, ideally, those you have collected from interested recipients. Messages that bounce and are marked as spam by recipients hurt your email reputation and make it more likely that future messages will be filtered.

  • Avoid purchasing email lists. Large commercial lists often contain bad and unused addresses. Sending to them can hurt your domain's reputation.

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