There are a number of reasons that can cause the "553 sorry, that domain
isn't in my list of allowed rcpthosts (#5.7.1)" error. The first item
to check is that your email client is configured properly.
Here is the link to our configuration page:
Our mail servers are configured to reject mail that is not hosted on our network, you can't send mail out from our servers with a "From" address that is not hosted on our network. This is to prohibit someone from trying to fake their "from" address. If you are using the wrong "from" address, the server will not allow you to send the message.
Another cause may be a misconfiguration of an IP address at your ISP. This is more common in Costa Rica, often for users of ICE DSL service.
See this page for more info: http://kb.blackcoralgroup.com/kblore/article.php?id=005
and also see below.
Next, the DNS for your IP address may be mis-configured. This also is a serious problem in Costa Rica for ICE clients.
FROM ONLY THE AFFECTED COMPUTER AT THE AFFECTED LOCATION (in other words this cannot be done remotely!)
1. Go to http://whatismyip.com
2. Record the IP address that is given to you.
3. Now go to: http://whois.net/reverse-dns-ip-lookup/
4. Enter the IP address from Step 2 into the box. ie 18.104.22.168
5. Look for this: 22.214.171.124.in-addr.arpa name = ip1-11-22-191.ct.co.cr. Note: This is a reverse of you IP and indicates all is correct.
Finally, you may not have an SPF record configured in your domain zone file. Some email servers are programmed to reject email from a domain not properly configured. Contact the company from which you purchased your domain name.