Dear Sir/Madam

thank you for your e-mail.

I’m currently out of the office, so I will have limited access to my e-mail. Please do not expect immediate answer.
I’ll be back in the office on [date].
In case your mail needs immediate attention please resend  it  to [substitute email] Att.: [substitute name]

If you need urgent assistance you can reach me on my mobile number [telephone number] (x GMT)

Thanks for your understanding.

Best regards,