|RCPT Hosts Error
There are two probable reasons this error might occur.
1) Lost Connection: An rcpt hosts file error occurs most often when your mail client has lost its connection to the Internet. Typically this can occur between the time you last checked mail and the time you try to send again. To correct the error, simply check mail again and then send your message.
Explanation of the error: In order to avoid allowing our mail server to be used as an open relay, we have a mechanism in place that essentially says you can't send mail unless you have logged onto the system as a valid user. The normal way to do this is by checking mail. This action sends your username and password to the server and logs you on. Then when you send mail, you are able to do so. However, if your connection breaks between the time you check and the time you send, you will not be recognized as a valid user and will receive the rcpt hosts error.
2)ISP Disallows SMTP: Your ISP may not allow you to use our SMTP server to send mail. If this is the case, simply use theirs. For example, Comcast users might use smtp.comcast.net rather than mail.yourdomain.com in their SMTP mail settings. Some SMTP settings for popular ISP's are as follows:
If you find it necessary to send legitimate messages to large numbers of people and your ISP does not allow you to do so, you can use our eBlast111 email marketing system to do so.
AT&T using an AT&T dial up: mailhost.worldnet.att.net
AT&T using another network: imailhost.worldnet.att.net
AT&T Business Internet Services: smtp1.attglobal.net or smtp2.attglobal.net
Bell Atlantic: outgoing.verizon.net
Cingular Mobile: mobile.mycingular.com
Free I.net: mail.nc.freei.net
IBM Global: smtp1.ibm.net
TDS Telecom: smtp.tds.net
Tesla Tech: smtp.tes-tech.net
Explanation of the error: Many ISPs have begun trying to do their part to control spam. Part of this effort is to limit the number of email messages their clients send at one time. They can only successfully do this if they make sure you can only send mail through their servers, so they turn off access to anyone elses SMTP servers except their own.