Some additional info. Tried to sniff what's going on using IPEX: ====- 8< -=================================================== 2006-09-16 16:24:26.330077 smtp2.rog.mail.vip.re2.yahoo.com:smtp >
myserver.name:55547 tcp AP S:663091283 A:2183648755 W:33304 (DF) 220 smtp106.rog.mail.re2.yahoo.com ESMTP 2006-09-16 16:24:26.330427 myserver.name:55547 >
smtp2.rog.mail.vip.re2.yahoo.com:smtp tcp AP S:2183648755 A:663091325 W:33304
(DF) EHLO myserver.name 2006-09-16 16:24:26.370257 smtp2.rog.mail.vip.re2.yahoo.com:smtp >
myserver.name:55547 tcp AP S:663091325 A:2183648776 W:33304 (DF) 250- smtp106.rog.mail.re2.yahoo.com 250-AUTH LOGIN PLAIN XYMCOOKIE
250-PIPELINING 250 8BITMIME 2006-09-16 16:24:26.370970 myserver.name:55547 >
smtp2.rog.mail.vip.re2.yahoo.com:smtp tcp AP S:2183648776 A:663091423 W:33304
(DF) MAIL FROM:<> BODY=8BITMIME 2006-09-16 16:24:26.409735 smtp2.rog.mail.vip.re2.yahoo.com:smtp >
myserver.name:55547 tcp AP S:663091423 A:2183648804 W:33304 (DF) 530 authentication required - for help go to
http://help.yahoo.com/help/us/mail/pop/pop-11.html

====- 8< -=================================================== Shouldn't Courier have issued "AUTH" instead of "MAIL FROM"?

esmtproutes: ====- 8< -=================================================== : smtp.broadband.rogers.com ====- 8< -===================================================

esmtpauthclient: ====- 8< -=================================================== smtp.broadband.rogers.com user...@rogers.com password ====- 8< -=================================================== (user...@rogers.com is the login name to be used. it does work with Postfix)

I've also tried adding the following to the esmtpauthclient: smtp2.rog.mail.vip.re2.yahoo.com user...@rogers.com password smtp106.rog.mail.re2.yahoo.com user...@rogers.com password

but it didn't make any difference

What else could I check here?