With Mailster you can send birthday greetings to your subscribers. All you need is the birthday as a custom field.

Goto Settings => Newsletter => Subscribers and add a new custom date field:

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delivery panel
Now create your birthday campaign and switch to the Autoresponder tab in the delivery panel.

Select “a specific user time” from the dropdown to reveal more settings.

To send your campaign every year select “1 year(s)”  based on the users “Birthday” value

To specific the time you have to set it up above. Since the birthday starts on Midnight (00:00) you have to set it to “12 hour(s) after” to send it twelve hours after midnight – on midday.

Save your campaign and you’re ready to go.

Keep in mind that users have to celebrate at least their first birthday to get this campaign and they will get it every year unless you have checked the “send campaign only once” checkbox