Trello does not allow you to specify a custom email link. The email address Trello gives you for the Email to Board feature include a secret that lets anyone who knows that address add cards to the board (or comment) as you. It's recommended you keep this email address secret and do not share it with others.
You could set up email forwarding with your email provider to your Trello email to board address if you wish though. How to do that would depend on your email provider - they very likely will have documentation on it.
Personally, I've added my email to board addresses as a contact, so I can just forward stuff to my Trello boards by typing the name, and my email client autocompletes it.
@Ron Rockwood if you're a Gmail user, you can also add cards to boards using the Gmail add-on:
Likewise I have a product that lets you use Trello as a Gmail client (so you can not only have cards for emails but can also reply to emails from Trello, and create new emails from Trello):
Other email options in Trello are:
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