Yahoo Accounts and Email Addresses
When you initially sign up for a Yahoo account you are assigned an email address. The email address is of the form:
Yahoo account name or ID@Yahoo.com
This email address created when you create your yahoo account becomes your primary email address, and cannot be deleted without deleting the yahoo account itself.
Your Yahoo account or yahoo ID gives you access to the yahoo network which currently consists of:
It is however possible to have more email addresses associated with the one yahoo account. This is achieved by adding an extra email address.
You can have only one extra email address, and it can be deleted whereas the main email account cannot.
The Extra email address feature was a way of combating spam by protecting the main email address. the idea being to use this extra email address instead of the main address.
Email sent to either address is sent to the same inbox, and if you got too much spam to the second email address you simply deleted it without the need to delete the yahoo account.
Once deleted you could then create a new extra (second) email address and use that one.
However this feature has been superseded by Disposable email addresses.
Disposable Email Addresses
Yahoo also offer Disposable Email Addresses which are basically email addresses that you use but can delete if they start to get spammed.
The idea is to use these addresses instead of your main email address when signing up for newsletters etc . Mail sent to these email addresses is forwarded to your main email
account just as if it were sent direct to the main email address.
Because the disposable address is not your main address you can delete it without affecting email to your main account.
Yahoo call this feature address guard and to configure it you need to create a base address that is used to create your disposable addresses.
You can then create multiple email addresses each using the same base. For example I want to create email addresses for two newsletters that I will sign up for; newsletter1 and
newsletter2, and my base address is swc. The two email addresses become:
swc-newsletter1@yahoo.co.uk and swc-newsletter2@yahoo.co.uk
Here is a screen shot of me creating a base address:

and of managing the disposable addresses. (note base address is different as swc was already taken, and so I had to choose another ( protectsteve )).

Disposable email addresses are very flexible and an excellent way of combating spam by protecting you main email address.