Mailstack
Sending Mailstack emails from Gmail
Sending Mailstack emails from Gmail
Mailstack mailboxes can be used to send emails from any service that allows emails to be sent via SMTP. This includes Google’s Gmail service.
In order to use this functionality you need to enable SMTP from your Google Workspace’s Admin console.
Go to Apps > Google Workspace > Gmail where you will find the following setting 
Enable this setting:
Now when you return to your Gmail client, go to the Accounts tab in the settings page and click 
Now add your Mailstack mailbox and name corresponding to that mailbox, depending on what settings you want for the alias, read this article, we recommend leaving it unchecked, especially if managing multiple users mail from your Gmail inbox:
Update the SMTP server to 
Once this has been added, all you need to do is click the link in the email sent to your Mailstack inbox to verify your account and you can now send emails from your Mailstack mailbox in Gmail!
Happy sending 💌
Allow per-user-outbound gateways:
Enable this setting:
Now when you return to your Gmail client, go to the Accounts tab in the settings page and click Add another email address in the Send mail as section:
Now add your Mailstack mailbox and name corresponding to that mailbox, depending on what settings you want for the alias, read this article, we recommend leaving it unchecked, especially if managing multiple users mail from your Gmail inbox:
Update the SMTP server to mail.hostedemail.com and use port 465 to encrypt your connection using SSL, finally adding your username (as full email) and password of your Mailstack mailbox.
Once this has been added, all you need to do is click the link in the email sent to your Mailstack inbox to verify your account and you can now send emails from your Mailstack mailbox in Gmail!
Happy sending 💌