Why my ex send me happy birthday congrats?

After an entire year—or almost—, without getting in touch, she suddenly send me an email, congratulating me for my birthday. We breakup years ago and I just don't get why she would even prefer emailing me, instead of using a social media. Or why she would even send me a happy birthday message, when she pushed me away. I was always open to the idea of keeping in touch with her, but why email? Is not like I am gonna be texting her on social media. You don't even have to follow someone, to send a text to them.

Since I am not experienced with relationships—she was my first—, should I even send her a happy birthday message on her birthday? Or skip it?

🤷?

Why my ex send me happy birthday congrats?
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