From the horses mouth
The CiviCRM Book has an excellent resource the reviews this idea completely:
Here is a very brief cliff notes version.
Recommended ways to send email
There are a lot of different ways to send an email. The two most common are:
- Start with Mailings -> New Mailing and then pick the group or groups to send email to (the best method for large groups of people)
- Do a search for contacts, select the ones you want, and choose "Send email to contacts" (the best method for small groups - avoids the whole CiviMail overhead and simply creates an activity for each person)
Don't do this...
A third approach, which is probably the most confusing and not one that we recommend, is a bit of a hybrid:
- Do a search for contacts, select the ones you want, and choose "Send/Schedule Mass Mailing".
This third approach is just like sending a CiviMail - except you can send to an arbitrary group of contacts rather than a pre-defined group. The reason it is confusing and not recommended is because it creates a "hidden" group based on the search results. Because the group is hidden, it can't be used to track unsubscribe requests. Therefore, when sending using this method you have to first create a group that will be used to track unsubscribe requests and then select this group when you send the mailing. This approach is very counter-intuitive and hard to maintain over time.