This email is in response to your query dated __/__/____ (date) regarding _________ (mention purpose). On behalf of _________ (name of the organization), I would like to formally apologize to you for sending an incorrect email by mistake. As discussed with the support team, we have mistakenly sent you that email and we regret the trouble it may have caused to you.
Therefore, we seek your apology regarding the same and we promise you that this mistake will not happen again from our end. If you need to discuss this further, you can always feel free to contact us at _________ (contact details).
___________ (Contact details)