The Birthday Gift module will send an email to the customer who has a birthday today, it can also create a discount voucher. You can set it to make vouchers or not, how much the voucher is worth, whether it's fixed or percentage value voucher, the duration of the voucher, and set the prefix of the voucher code. You can set whether or not to send to all users, or just users with a valid order, also pick if the customer needs to have enabled newsletters, and set for which user groups will get the voucher/email. The module will log the emails sent, showing you stats on how many emails were sent, and how many vouchers used. This module works with eschiendorfer's Krona module.