Hello,

If you want to use macros in your email template, you need to define them frist. You can do that in the ~\CMSWebParts\Membership\Registration\CustomRegistrationForm.ascx.cs file (or ~\CMSWebParts\Membership\Registration\RegistrationForm.ascx.cs -> depends on web part you are using) and there is following code around the line 757:

replacements = new string[4, 2];
replacements[0, 0] = "firstname";
replacements[0, 1] = ui.FirstName;
replacements[1, 0] = "lastname";
replacements[1, 1] = ui.LastName;
replacements[2, 0] = "email";
replacements[2, 1] = ui.Email;
replacements[3, 0] = "username";
replacements[3, 1] = userName;

And here you can define your custom macro, which will be used in your template and where the first field is a name of a macro and the second is its value.

Best regards,
Jan Hermann