Overview
Please note, the Mailgun integration is only available to users on a Basic, Professional, or Custom plan. If you are on a free plan or a free trial and want to upgrade, check out our pricing page or reach out to the Apollo Sales Team for more information.
If you use Mailgun to send high volumes of emails, you can integrate your account with Apollo. This means that you can avoid sending messages directly from your connected mailbox in Apollo to bypass the regular email provider sending limits. As a result, you can send more emails without negatively impacting your domain's deliverability ratings.
Refer to the sections below for the steps to integrate your Mailgun account with Apollo.
Please note, if you created your Mailgun account with a domain from an EU server, unfortunately, you cannot currently integrate your Mailgun account with Apollo.
Connect Your Mailgun Account to Apollo
Please note, before you can integrate Mailgun with Apollo, you need a Mailgun account. If you do not have an account, you can sign up here. For more information about getting started with Mailgun, please refer to the Getting Started section of the Mailgun Knowledge Base.
Once you have set up a Mailgun account, launch Apollo, click Settings, and then click Integrations under the "Configurations" section on the left.
Scroll to Mailgun and then click Connect.
Fill in your Mailgun primary account API key and click Link API key.
Please keep in mind that the primary account API key must be a private key. If you're not sure where to find your key, fear not! Mailgun has got you covered! Check out the Where Can I Find My API Key and SMTP Credentials? article on the Mailgun Knowledge Base. Please also note that Apollo does not support Mailgun domain sending keys. For more information about the different API keys in Mailgun, read this section of the Mailgun API Reference Guide.
You have now connected your Mailgun account to Apollo.
Add Mailgun Webhooks for Your Domains
This is an important step, folks! To ensure full functionality of the Mailgun integration, you need to add a webhook for each domain that you use to send emails from in Apollo. But don't worry, it's not as scary as it sounds. Follow the simple steps below, and voila! Like magic, you can start tracking the performance of your sequences and identify bounced emails with accuracy to improve your email deliverability rates.
Now that you have connected Mailgun, Apollo displays all the domains connected to your Mailgun account.
Click Add tracking next to each of the domains that you want to connect.
You have now added a Mailgun webhook to Apollo.
You can delete a connected webhook from Apollo at any time. To do so, click Remove tracking.
Please note, Apollo only automatically pulls in the list of domains from Mailgun when you first integrate Mailgun with Apollo. This means that if you add or delete a domain in Mailgun, the change does not immediately reflect in the list of domains in Apollo. However, no need to panic! If you make any changes in Mailgun, you can click Refresh List. Apollo then refreshes the list as well as the status of the Mailgun webhook in Apollo. 
If you try to add or remove a webhook from a domain that no longer exists in Mailgun, Apollo displays an error message.
Deleted the wrong domain? You'll need to reconnect the domain in Mailgun before you can add the Mailgun webhook in Apollo. For more information about how to add and delete domains in Mailgun, hop into this article in the Mailgun Knowledge Base.
Please note, you can only connect 1 webhook per domain with the Apollo<>Mailgun Integration. If you encounter the error below, you can either delete a non-Apollo webhook from Mailgun or manually add the webhook in Mailgun. 
For more information about how to add or delete webhooks in Mailgun, please refer to the Guide to Using Mailgun Webhooks in the Mailgun Knowledge Base. Alternatively, you can use another domain instead.
Enable Mailgun for a Mailbox
Click Settings. Then, click the Mailboxes tab in your Personal Profile.
Click the Additional Options (...) button to select the mailbox that you would like to enable with Mailgun. Then, click Send emails from Mailgun.
You have now enabled Mailgun for a mailbox in Apollo.
Please note, you can stop sending emails from Mailgun at any time. To do so, click the Additional Options (...) button again and then click Stop sending emails from Mailgun.
Confirm You're Set Up
To confirm that you've integrated Mailgun correctly, launch Apollo, click Settings, and then click the Mailbox tab.
You will see Send From Mailgun below the default email address. This confirms that you have set up Mailgun correctly in Apollo.
Maximize Your Daily and Hourly Send Rates
Now that you have connected your Mailgun account to Apollo, you can safely maximize your daily and hourly send rates, without risking your domain reputation.
To do so, click Settings. Then, click manage sending limits under each linked Mailbox.
Click the mailbox for which you want to adjust the sending limits.
From here, you can adjust the Daily Sending Limit and the Maximum # of Emails to Send Per Hour.
Please note, the email sending limits with the Mailgun integration are 6000 per day and 500 per hour. If you need more, you can add additional mailboxes to increase sending limits. For more information on sending limits in Apollo, please read the Email Sending Limits Overview article.
You have now maximized your email-sending limits in Apollo.