It does not matter if you send messages from Outlook Express running in a workstation in your LAN or from your WAMP server. The ISP is usually worried about you sending heaps of messages directly from your server, in other words, if you are sending SPAM. Your agreement with your ISP probably states how many messages with similar content you can send in a given time period. If you send more, you will be in breach of your agreement. Many ISPs also block TCP port 25 so that you can only send messages via their STMP server.
Your application needs to validate the format of the email addresses. You cannot easily check much more because of the limitations of the getmxrr() and checkdnsrr() functions in the Windows implementation of PHP, for more info check the PHP manual at
[
php.net], but, as the manual points out, you may be able to do the checks using the PEAR class Net_DNS.
Regards,
toivo
Sydney, Australia