It is good Netiquette to respond to ads with phone numbers only. Don’t trust someone who won’t give you their phone number.
Contact Number Netiquette Classifieds
Phone numbers give a person responding to an online classified the ability to contact someone about a post directly. A phone call can be hard to ignore. Those who post Classifieds with phone numbers are more accessible than those with email only.
Classifieds Contact Number
The accessibility a phone number provides gives a seller more credibility. An email message is asynchronous communication. The recipient may not respond immediately or at all.
When an online classified advertisement has an email address only it means they are screening responses to the ad. The person posting does not trust the responses. The lack of trust can be for legitimate reasons. An email address without a phone number in an online classified advertisement is a red flag.
Contact Number Netiquette
Respond to posts with phone numbers because the advertiser is accessible.