Other Mailing systems have no trouble with that. I have not modifyed the scripts.
Turn on session logging in MercuryS to verify what is coming in from your PHP script. If this script is sending <<user@domain>> in the MAIL FROM: and RCPT TO: addresses then every valid SMTP/ESMTP server is going to have problems with this PHP script. Quite possibly you have entered the e-mail addresses with the <> and then the sending script is adding the <> as well.
Here a valid MercuryS session log without the actual data part. This is coming from GMail where this server is being used as the SMTP host for GMail. I've munged the authentication username and password.
20:58:21.859: Connection from 209.85.217.209, Sun Oct 18 20:58:21 2009<lf>
20:58:21.859: << 220 tstephenson.com ESMTP server ready.<cr><lf>
20:58:21.968: >> EHLO mail-gx0-f209.google.com<cr><lf>
20:58:21.968: << 250-tstephenson.com Hello mail-gx0-f209.google.com; ESMTPs are:<cr><lf>250-TIME<cr><lf>
20:58:21.968: << 250-SIZE 0<cr><lf>
20:58:21.968: << 250-AUTH CRAM-MD5 LOGIN<cr><lf>
20:58:21.968: << 250-AUTH=LOGIN<cr><lf>
20:58:21.968: << 250-STARTTLS<cr><lf>
20:58:21.968: << 250 HELP<cr><lf>
20:58:22.203: >> STARTTLS<cr><lf>
20:58:22.203: << 220 OK, begin SSL/TLS negotiation now.<cr><lf>
20:58:22.468: [*] SSL/TLS session established: 3DES, CBC mode, keysize 192 bits
20:58:22.578: >> EHLO mail-gx0-f209.google.com<cr><lf>
20:58:22.578: << 250-tstephenson.com Hello mail-gx0-f209.google.com; ESMTPs are:<cr><lf>250-TIME<cr><lf>
20:58:22.578: << 250-AUTH CRAM-MD5 LOGIN<cr><lf>
20:58:22.578: << 250-AUTH=LOGIN<cr><lf>
20:58:22.578: << 250 HELP<cr><lf>
20:58:22.703: >> AUTH LOGIN<cr><lf>
20:58:22.703: << 334 VXNlcm5hbWU6<cr><lf>
20:58:22.812: >> ddXNlcj2U1Mlw==<cr><lf>
20:58:22.812: << 334 UdGFzcl3dvc3mQ6<cr><lf>
20:58:22.906: >> cGdFzclzE4O2DM=<cr><lf>
20:58:22.906: << 235 Authentication successful.<cr><lf>
20:58:22.031: >> MAIL FROM:<thomas@tstephenson.com><cr><lf>20:58:22.031: << 250 Sender OK - send RCPTs.<cr><lf>
20:58:23.140: >> RCPT TO:<techsupp@tstephenson.com><cr><lf>20:58:23.140: << 250 Recipient OK - send RCPT or DATA.<cr><lf>
20:58:23.234: >> DATA<cr><lf>
20:58:23.234: << 354 OK, send data, end with CRLF.CRLF<cr><lf>
<blockquote>Other Mailing systems have no trouble with that. I have not modifyed the scripts.</blockquote><p>Turn on session logging in MercuryS to verify what is coming in from your PHP script.&nbsp; If this script is sending &lt;&lt;user@domain&gt;&gt; in the MAIL FROM: and RCPT TO: addresses then every valid SMTP/ESMTP server is going to have problems with this PHP script.&nbsp; Quite possibly you have entered the e-mail addresses with the &lt;&gt; and then the sending script is adding the &lt;&gt; as well.
</p><p>Here a valid MercuryS session log without the actual data part.&nbsp; This is coming from GMail where this server is being used as the SMTP host for GMail.&nbsp; I've munged the authentication username and password.
</p>20:58:21.859: Connection from 209.85.217.209, Sun Oct 18 20:58:21 2009&lt;lf&gt;
20:58:21.859: &lt;&lt; 220 tstephenson.com ESMTP server ready.&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &gt;&gt; EHLO mail-gx0-f209.google.com&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250-tstephenson.com Hello mail-gx0-f209.google.com; ESMTPs are:&lt;cr&gt;&lt;lf&gt;250-TIME&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250-SIZE 0&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250-AUTH CRAM-MD5 LOGIN&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250-AUTH=LOGIN&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250-STARTTLS&lt;cr&gt;&lt;lf&gt;
20:58:21.968: &lt;&lt; 250 HELP&lt;cr&gt;&lt;lf&gt;
20:58:22.203: &gt;&gt; STARTTLS&lt;cr&gt;&lt;lf&gt;
20:58:22.203: &lt;&lt; 220 OK, begin SSL/TLS negotiation now.&lt;cr&gt;&lt;lf&gt;
20:58:22.468: [*] SSL/TLS session established: 3DES, CBC mode, keysize 192 bits
20:58:22.578: &gt;&gt; EHLO mail-gx0-f209.google.com&lt;cr&gt;&lt;lf&gt;
20:58:22.578: &lt;&lt; 250-tstephenson.com Hello mail-gx0-f209.google.com; ESMTPs are:&lt;cr&gt;&lt;lf&gt;250-TIME&lt;cr&gt;&lt;lf&gt;
20:58:22.578: &lt;&lt; 250-AUTH CRAM-MD5 LOGIN&lt;cr&gt;&lt;lf&gt;
20:58:22.578: &lt;&lt; 250-AUTH=LOGIN&lt;cr&gt;&lt;lf&gt;
20:58:22.578: &lt;&lt; 250 HELP&lt;cr&gt;&lt;lf&gt;
20:58:22.703: &gt;&gt; AUTH LOGIN&lt;cr&gt;&lt;lf&gt;
20:58:22.703: &lt;&lt; 334 VXNlcm5hbWU6&lt;cr&gt;&lt;lf&gt;
20:58:22.812: &gt;&gt; ddXNlcj2U1Mlw==&lt;cr&gt;&lt;lf&gt;
20:58:22.812: &lt;&lt; 334 UdGFzcl3dvc3mQ6&lt;cr&gt;&lt;lf&gt;
20:58:22.906: &gt;&gt; cGdFzclzE4O2DM=&lt;cr&gt;&lt;lf&gt;
20:58:22.906: &lt;&lt; 235 Authentication successful.&lt;cr&gt;&lt;lf&gt;
<b>20:58:22.031: &gt;&gt; MAIL FROM:&lt;thomas@tstephenson.com&gt;&lt;cr&gt;&lt;lf&gt;</b>
20:58:22.031: &lt;&lt; 250 Sender OK - send RCPTs.&lt;cr&gt;&lt;lf&gt;
<b>20:58:23.140: &gt;&gt; RCPT TO:&lt;techsupp@tstephenson.com&gt;&lt;cr&gt;&lt;lf&gt;</b>
20:58:23.140: &lt;&lt; 250 Recipient OK - send RCPT or DATA.&lt;cr&gt;&lt;lf&gt;
20:58:23.234: &gt;&gt; DATA&lt;cr&gt;&lt;lf&gt;
20:58:23.234: &lt;&lt; 354 OK, send data, end with CRLF.CRLF&lt;cr&gt;&lt;lf&gt;