Note that SBC Yahoo! has a delivery limit of 1,000 messages per day and 50 messages per session. Some users have had problems at 950 message per day and more than 25 messages per session though.
Last minute: it seems SBC is closing SMTP access as soon as you send the same message to at least 30 recipients. The solution is to ask SBC to unlock port 25 on your account so you can use a third party server (e.g. your website server).
As a precautionary measure to stop spam, many ISPs are no longer allowing outbound traffic on port 25. As a result, your ISP may have blocked port 25 on your account. Port 25 is the standard TCP port used to send e-mail via the SMTP protocol. Hopefully most SMTP servers offer their services through several ports. So, if MaxBulk Mailer can't connect to your server through default port 25 try to use port 587 or 2525.
Important: Usually the Yahoo SMTP server is deactivated by default until you verify your Yahoo-SBC email address. If the 'LOGIN' authentication scheme gives problems try 'PLAIN' from the second pull-down menu next to 'Authentication'.
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