It depends on what email system you are using and therefore what determines if something is spam.
Most mail providers, hotmail, BT, Yahoo will have filters in place that decide if an email is spam and these are always changing. You have to keep monitoring your spam box and "teach" the mail system that certain items are not spam.
I know that Yahoo decided that mail with all uppercase subjects looked dodgy and therefore marked them as and it maybe the your mail provider things A4A looks dodgy all of sudden.
If you mark the A4A email sender as a "safe" sender you should not have this problem again.
