My husband and I each have a bt email address, recently we are being asked for two factor authentication for each of our emails. The problem is the codes are being sent to the same mobile phone number (my husband's mobile) so I can't access my email unless he is here with his phone. Is there anyway to specify separate phone numbers for each email address even though we only have one BT accounts?
Only one phone number and email address can be used for all the email accounts that were created from your husbands broadband account and which he still manages.
I suspect that you have just been given one of the email accounts from your husband's broadband account by him. As such he is still the "owner and manager" of the email account and because of this the 2FA PIN gets sent to his phone.
If your husband had "gifted" the email account to you using the correct BT method as per the following link you would have had to set up your own BTID and MyBT in order to accept the email account and you would then become the "manager" of the email account which would then allow you to enter your own email address and phone number in the MyBT section "Your Details" > "Personal Details" > "Contact Details".
He can still "gift" the email account to you if you want to manage it your self.
See link and sub links