Why aren't my emails going through? i am getting blocked out of the blue by gmail, hotmail, att worldnet?

the gmail/hotmail failure messages seem to think i'm spamming-- i'm sending a message to the parents in my fifth grader's class-- the attworldnet said i was blocked for "abuse"-- this is my best friend's address for many years. nothing has changed vis-a-vis my email or the kind of messages i'm sending, but lately i can't seem to get through without resending several times. what's up?
Why aren't my emails going through? i am getting blocked out of the blue by gmail, hotmail, att worldnet?
If you read the Failure notice it will tell you. Other wise I can ramble on all day about


why you got a failure notice.


1. Temporary Suspended Account. From either Sender or receiver.


2. Cancelled account.


3. Full email box.


4. Your on a botnet with a virus and the server returned it because your ISP has stopped


letting you send email until the PC is cleaned of botnet virus.


5. Wrong email address or domain of recipients.


6. Too many email addresses on one sending.


7. One address needs to be corrected before any on a multiple list can be sent.


8. The message took too long and can`t find address so one of the servers gave up.