Here is a Python solution using regular expressions to extract the valid email addresses: ```python import re text = "Contact information:\n1. John Doe - john.doe@example.com\n2. Jane Smith - jane@smith-family.net\n3. support@company.co.uk\n4. info@subdomain.example.org\n5. Invalid email: not.an.email.com\n6. Another invalid: @missing-username.com" emails = re.findall(r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b', text) print(','.join(emails)) ``` This will output: ``` john.doe@example.com,jane@smith-family.net,support@company.co.uk,info@subdomain.example.org ``` The regular expression used here is a common pattern for matching email addresses. It matches strings that start with one or more alphanumeric characters, followed by a '@' symbol, followed by one or more alphanumeric characters, a period, and finally two or more alphabetic characters.