Attained last year then you retained this year.

Attained you get the email when you attain the status

Retain then you get it at year end, assuming you do not attain a higher status before that

if you are feb year end and retain silver you will get that 'congrats' email in feb. If you retained silver last year you would have received the email in feb this year. If you attained silver earlier in the year you would have received the email when you attained it