Reusing the email address is not possible. Every subscription is attached to a Joomla user created for it. Joomla requires a different email address for each user.
You do not have to create a new mailbox for each of your clients. A mail forwarder will work just fine. For example, you can have email@example.com and firstname.lastname@example.org forward the emails to email@example.com or even firstname.lastname@example.org.
Also, if you have a GMail account, e.g. email@example.com, you can use addresses like firstname.lastname@example.org, email@example.com etc. They all route the email to the original email address. This also works if you are using Google Apps on your domain.
So my suggestion is to create a simple GMail account and use the +something trick in the email address to create a practically infinite number of unique email addresses which all route to the same GMail inbox.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!