TypeScript export/import function

I have a module I wrote (which is installed via npm from a private repo) that the following structure:

email.ts, utils.ts, index.ts, (some other files)

On my email.ts I have the following function:

export default function sendEmail(toEmail: string, subject: string, content: string): any {

    let helper = SendGrid.mail;

    let from_email: any = new helper.Email(process.env.FROM_EMAIL);
    let to_email: any = new helper.Email(toEmail);
    let helperContent: any = new helper.Content("text/plain", content);
    let mail: any = new helper.Mail(from_email, subject, to_email, helperContent)

    var request = SendGrid.emptyRequest({
        method: "POST",
        path: "/v3/mail/send",
        body: mail.toJSON()
    });

    //This performs the request with a promise
    SendGrid.API(request).then((response: any) => {
        //Deal with output as needed
        console.log("email was sent!!");
    }).catch((err: any) => {
        //log.error(err);
    });
}

Then, on my index.ts I have the following declarations:

export * from "./email";
export * from "./errors";
export * from "./logger";
export * from "./objectUtils";
export * from "./queryFilter";
export * from "./templateEngine";
export * from "./utils";

On the application where I import this module I import this as

import * as Utils from "my-utils";

Finally, whenever I want to use the sendEmail function, I call it by using this statement:

Utils.sendEmail(email, subject, content);

However this always throws an error stating that "Cannot read property 'sendEmail' of undefined".

Why is this happening? Shouldn't I be able to use this type of declarations when exporting this way? What is the solution for this?

Best Regards