There are so many potential things that could be happening here.
The attacker may try phishing by having you click a malicious link which containing malware such as keyloggers or similar. The attacker could also try social engineering to gather all information he/she can about you before attempting to get into your account. Keep in mind most e-mail servers will include the originating IP when sending e-mail so they could get your IP and attempt to hack into your computer. The spammer may be just gathering active e-mail to send spam later down the line. 

 - [Phishing](https://en.wikipedia.org/wiki/Phishing)
 - [Social Engineering](https://en.wikipedia.org/wiki/Social_engineering_%28security%29)