Possible to add Sender domain?

Hi,

We are using SMTP Mailer together with MailGun and would like to be able to specify the ‘Sender domain’ in addition to the ‘From Email Address’.

Is this possible?

For reference, please see: https://help.mailgun.com/hc/en-us/articles/202236494-What-is-the-difference-between-the-From-and-Sender-

Thank you.

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