There would be a database with all subscriptions (e-mail addresses and the corresponding scheme ID). Once an e-mail is sent for a scheme, a "send_email" bool value would be turned to "off". The scheme link in the sent e-mail should re-enable the "send_email" value; another link in the e-mail and on the scheme viewing page should allow unsubscribing.
Also try saving the language in use to send an e-mail in the appropriate language.
Later, try directly redirecting to the first unread comment.
There would be a database with all subscriptions (e-mail addresses and the corresponding scheme ID). Once an e-mail is sent for a scheme, a "send_email" bool value would be turned to "off". The scheme link in the sent e-mail should re-enable the "send_email" value; another link in the e-mail and on the scheme viewing page should allow unsubscribing.
Also try saving the language in use to send an e-mail in the appropriate language.
Later, try directly redirecting to the first unread comment.