"Sender verify failed" when sending email?

[Jeff75]

Can someone tell me what these two different errors mean? Are these spammers trying to send mail using a script or an email client?

2006-12-14 07:18:16 H=(61-59-188-119.adsl.static.seed.net.tw) [61.59.188.119] F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed

2006-12-14 06:49:40 H=(KD125054027172.ppp-bb.dion.ne.jp) [125.54.27.172] F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed

Most of the errors above are have foreign hostnames from countries like thailand, japan, england, taiwan. They are US based and only deal with US based clients. Is this a spammer tryign to send mail through their account?

2006-12-14 07:41:33 1Guptx-000B6m-6e H=(49.222.190.220.broad.wz.zj.dynamic.163data.com.cn) [220.190.222.49] F=<[email protected]> rejected after DATA: syntax error in 'From:' header when scanning for sender: domain literals not allowed in "" Roberts" <[email protected][VAR999.0]>"

 

[tweakservers]

the sender email address can be easily spoofed on nowadays spams

 

[mitul]

Because your server cannot verify that [email protected] is valid (or remotehost.com is a valid domain, depending on how you have sender verify set).

There are number of posts on this forum for the same issue. You should try digging them for more information.