Why can't i send email from my yahoo account?

i have been having very similar problems all week with sending emails from my yahoo account. some outbound messages go fine, but in too many cases i can't send a message. Either I get prompted for captchas constantly or, like you, I get a message saying they've detected a possible issue (i.e., spam) and can't send the email and to try again in 24-hrs. in many cases, even after answering the captchas correctly, it still won't send and gives me the spam message.

At this point, I have no idea if any particular email will get sent or get blocked. My account is unusable like this.

i have sent many emails to tech support, but have not gotten any useful response. So I went to their online chat and was talking to an agent for 30 minutes or so.

The conclusion from the chat is that i have been advised to send no more than 2-4 emails per day which contain any of the following: "HTML code (code used to format websites), Links to other websites, Embedded graphics, Attachments, Forwarded messages (chain letters, jokes, etc.), High Outbound Message Volume, Sending email to multiple recipients." Since 90% of modern email fits into one or more of these buckets, this is wildly impractical.

As the message indicates, I was told that the account will clear after 2-24 hours, but this has not been the case for me. For several days running, I have had a large percentage of perfectly normal messages blocked. But then even if it does clear, the rep confirmed that the "2-4 emails per day max" rule still applies.

Based on my experience and what the rep said, it sounds like Yahoo is clamping down so hard on spammers that normal email usage has now become suspect and subject to blockage.