How to delete all accounts registered with my email?

NO.....you should have written them down somewhere. When I first started I would not have either. Anyway just delete those that you can remember and hope for the best. You also have the option of deleting this account and creating a new one.

To close your account make sure that you are signed
in to the account that you wish to delete.

Special attn: Make sure you read what you will LOSE when you
cancel your account.
https://edit.yahoo.com/config/delete_user?.scrumb=qPzkC.wTcVq
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On the sign in page click on CREATE NEW ACCOUNT located at
the bottom of the sign in area. OR Click this link and fill out the form
to create a new account.
https://edit.yahoo.com/registration?.int...
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Email ID requirements/restrictions

http://help.yahoo.com/kb/index?y=PROD&page=content&id=SLN3015&actp=search&viewlocale=en_US&searchid=1372700122886&locale=en_US&y=
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MOBILE PHONE NUMBER REQUIRED
http://help.yahoo.com/kb/index?y=PROD&page=content&id=SLN14992&actp=search&viewlocale=en_US&searchid=1373569187669&locale=en_US&y=
NOTE: I have found that if you enter your home phone (land line) instead of a Mobile phone number the next screen will tell you they recognize it but you can continue and verification will go through your home phone.
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Password requirements
http://help.yahoo.com/kb/index?y=PROD&page=content&id=SLN5681&actp=search&viewlocale=en_US&searchid=1372603048275&locale=en_US&y=
.
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NOTE: You can make as many ID's as you want.

Recommendation: Create a STRONG password for each.
https://help.yahoo.com/kb/index?page=content&id=SLN3012&actp=search&viewlocale=en_US&searchid=1372466487751&locale=en_US&y=PROD_MAIL_ML
NOTE:..creating a strong password makes it more difficult to
hack your account...=))
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And some VERY good secret questions/answers.
http://help.yahoo.com/kb/index?page=content&id=SLN2031&actp=search&viewlocale=en_US&searchid=1353160463996&locale=en_US&y=PROD_ACCT
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And PLEASE write them down somewhere in
case you forget them. I have seen many users report they cannot
remember them, which creates problems when trying to recover
forgotten ID'S and Passwords. =))
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If you have not done this this step may help you when your account
has been compromised...Strongly recommended

Setting up your second sign-in verification
http://help.yahoo.com/kb/index?page=content&id=SLN5013&locale=en_US&i=6MgfobltdzLLFpAeSV/ocg==

Note: Once you setup this option, you or the person setting up this
option on his/her account must and should access his/her account
using only the computer used to setup this verification. If he or she
logs into another system or computer he/she will be asked to verify
their identity using the security questions. if someone tries to HACK
in to your account they will have to answer these question.

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Yahoo no longer picks the best answer. We out here would
appreciate YOU doing it. So....when you are done receiving
answers to your question "PLEASE" pick one as a BEST
answer so someone out her can get credit for answering your
question...... Thanks......

You must wait ONE HOUR after you ask a question before choosing.

This link will show how.
https://help.yahoo.com/kb/answers/SLN8284.html?impressions=true



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