I appreciate your email. Currently, I am out of the office but will return after (Date of Return). My access to email will be limited during this period of time.
Rather than clutter your general greeting, set an auto-attendant for a campaign-specific phone number. You can assign a unique number to each of your campaigns. Record a voicemail message that helps callers to learn more about your marketing campaign.

So, for whatever reason you’re out of the office, your email inbox should be informative with any information about office closures or unexpected absences: Include an expected return date and time. Offer alternative point of contact and their details. Add the general office contact number and email address if you don’t have a specific point of contact. Be friendly and warm in your tone, even if you choose to keep it simple.
Plus, he incorporated a delightful technique to let people know that if they really wanted him to read their emails, they should probably send them again after his return. Not only does that keep the sender accountable by saying, "If this is really important, you know when to reach me," but it also helps him truly vacate his work while he's away. And that's hard to do.