> ## Documentation Index > Fetch the complete documentation index at: https://docs.upflow.io/llms.txt > Use this file to discover all available pages before exploring further. # Sending emails - Configure a subdomain > Send Upflow reminders through a Mailgun subdomain when your main domain is already in use, including DNS verification and required email routing rules. If you are already using Mailgun internally, this option is for you. This will allow you to send emails via your domain and use email tracking. In that case, you will be using **billing.mycompany.com** instead of **mycompany.com** to send emails. The process is similar to the main domain process, with the added step of adding email routing to your regular email addresses. ## Configure your DNS Once you have decided which subdomain you want to use (e.g. billing.mycompany.com) follow the steps described in [this article](/en-us/collection-and-collaboration/emails/sending-emails-configure-your-domain) to verify the subdomain ownership. ## Set up email routing to your regular email addresses To receive customer replies at your usual email address, you will need to (1) add the subdomain to your email account. And (2) assign the subdomain addresses as a new alias for the users. * [Here's how to do it for Gmail accounts](https://support.google.com/a/answer/7502379?hl=en#zippy=%2Cadd-a-domain-alias-give-users-an-address-at-another-domain). * [Here's how to do it for Microsoft accounts](https://learn.microsoft.com/en-us/microsoft-365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide)