Have tried to delete one of my email accounts in talktalk mail but for sme reason talktalk have removed the delete link/delete option. Looking at the comunity forum it has been like it for a long time.
User deletion of mailbox email addresses is not currently available but you can give instructions for mailbox deletion to the TalkTalk Data Protection Office team.
See the GDPR help page item 'Your Right to be Forgotten / Right to Erasure '. There's a postal address, which in my view is the best way to contact the Data Protection team, but you can initiate a contact via any of the TalkTalk contact methods.
