Can I send automatic, scheduled e-mails about expiring or just-expired memberships?
Multiple scheduled reminders are already possible out of the box using the &quot;Scheduled Reminders&quot; feature.
From the online book:

Creating and managing scheduled reminders
Scheduled reminders can be created from the administration page at Administer &gt;
Communications &gt; Schedule Reminders or during the creation of an
event.
From the administration page:

Click on Add Reminder.

Give your reminder a name that will help you identify it if you need to edit it in the future.

Select an entity for your scheduled reminder. This will bring up a further set of options relevant to that entity: activities have
activity types and statuses; membership gives membership types and
statuses, and so on. These secondary options are (usually)
multi-select fields, so you can choose to include more than one option
in each field.

Choose when to send the reminder. This can be a set date or an amount of time before or after the start or end of your chosen entity.

If you want to send more than one reminder, check the Repeat box. This gives you choices about the interval of repetition and when the
repetition should end.

Check Record activity for automated email if you want a record of the contacts who received this reminder.

Fill in From Name and/or From Email if you don't want this reminder to come from the default name and email address for your
site.

Refine or add to your recipient list. For more about your choices, see Limiting or adding to your recipient list in this chapter.

Choose to send your reminder as an email, an SMS or either depending on the preferred method(s) of communications for the
contact.

Compose your message. You can use Message Templates or write the message from scratch. Note that you cannot save your message as a new
template or modify an existing template from this screen, so if you
are writing a reminder for the first time and you think you will want
to re-use it, consider creating it as a Message Template instead.

Click Save when you are are done.


Reminders can be edited, disabled, or deleted from Administer &gt;
Communications &gt; Schedule Reminders.
IMPORTANT: Your system administrator will need to ensure that the
Send Scheduled Reminders scheduled job is enabled and runs at least once a day. Refer to the Scheduled Jobs chapter for configuration
details.