His emails come back, undelivered, citing 'system error' or 'unknown address'.
Still unwilling to risk it all, he's tried just walking in at a normal pace. He made it to reception once, before being escorted out by security. Now, the doormen know his face and stop him on sight.
So Clark writes letters. He's sent one nearly every day for a year. He doesn't worry about licking the stamp.
At the Luthorcorp penthouse, Lex reads each letter, sometimes twice.
After that, he burns them.
For redeem147's unrequited prompt.