ldc-web/app/Models/EmailAddress.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class EmailAddress extends Model
{
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'account', 'password',
        'domain_name_id'
    ];

    // * METHODS

    /**
     * domain_name getter
     *
     * @return mixed
     */
    public function getDomainNameAttribute()
    {
        $dn = DomainName::findOrFail($this->domain_name_id);
        return $dn->utf8_name;
    }

    // * RELATIONSHIPS

    /**
     * BelongsTo domain name relation
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function domainName()
    {
        return $this->belongsTo(DomainName::class);
    }
}