Including even a passing reference stating that your customer’s email is important to you shows your appreciation for the message that you are currently unable to respond to.
I think that’s on the person who covered for you –presumably they are in your department. If I take care of a client for Fergus while he’s out, I let him know the problem that came in, solution, and any still pending information. Emailer emails Vickie. May not just forward the message that they sent to or received from me. Vickie gets these kinds of questions every day, doesn’t know it has anything to do with me, just answers the question. I get back, see the message, and may not realize Vickie has already handled it. That’s not Vickie’s fault. I think ENFP in Texas has it right above – before starting the work, you can ask the sender if they still need this.

One may also ask, how do you write a holiday notice? Holiday Notice Letter Writing Tips Specify the duration of leave and name of the colleague who will handle your work responsibilities in your absence. Furnish contact details for any urgent requirement and mention your date of joining back work. I will be out of the office starting (Starting Date) through (End Date) returning(Date of Return). If you need immediate assistance during my absence, please contact (Contacts Name) at (Contacts Email Address). Otherwise I will respond to your emails as soon as possible upon my return. Include the date of your return. Let people know of any other individuals they can contact for help in your absence. If people typically contact you for a certain type of information or approval, let readers know how they can find the information or get the approval in your absence. How do you write a professional out of office message?
With emojis looking different on nearly every operating system and brand of smartphone, this is a bold choice which could leave your emailers confused. Are you crying with laughter or wailing with existential dread? Hard to tell.