Is there any way to retieve emails that have been accidentally deleted from my inbox?
First place to check is in the trash box.
If you are on the BTYahoo system you can follow this link.
If you are on the BTMail system and if they are not in the trash folder you can not recover them.
If you access your emails on more than one device using an email client and you have the email client set up as a POP3 account you may find that the email is still in the inbox on that device.