Emails shown in mailing reports are primary accounts and not the recipient email
The email address listed in mailing reports is the 'primary' email address for the contacts mailed. This is regardless of whether the mailing was sent to the 'primary' email address or if an alternative email had been selected.
Eg. contacts have work addresses listed as 'primary' and personal addresses listed as 'home'. The mailing is sent to 'home' email addresses, but the emails listed in the report are the 'primary' emails. This gives a false representation to the user of which email address the mailing has gone to.