Free download from: http://www.magsys.co.uk/delphi/magics.asp
This new ICS component has been used in our ComCap application to send emails for the last three months. Magenta Systems Mail Queue Component has two main benefits over a simple TSslSmtpCli component: it supports extended retries over many hours or days, and supports multiple SMTP relay servers, while alleviating the need for the application to handle retries. The component also allows HTML mail to be sent using SSL, something THtmlSmtpCli does not currently support. Mail is queued to disk, so retries will continue if the application is restarted. TMagMailQueue is designed to prepare, queue and send email. Preparing the email is done using the ICS THtmlSmtpCli component so it may be plain text or HTML email with one or more file attachments. Once the mail properties in QuHtmlSmtp have been specified, it is queued using the QueueMail method which saves it to an EML spool file. The component runs a thread which checks the queue for new EML spool files, and attempts to forward them to one or more SMTP Mail Servers using TSslSmtpCli, optionally with SSL. If mail delivery succeeds, the spool file may be deleted or moved to an archive folder. If mail delivery fails, the spool file remains in the queue and further attempts are made separated by the times in minutes listed in the RetryList list. If all delivery attempts fail, the spool file may be deleted or moved to a badmail folder. Note that some email servers support grey listing and reject the first email attempt from a new sender but allow a retry 10 or 15 minutes later, something that is very effective in blocking spam emails (since they don't usually retry). If multiple mail servers are specified, delivery is attempted once using each server, for each retry attempt. Each mail server is specified as TMailServer and there is no limit to the total. Each time the queue is updated or a delivery attempt made, the queue is saved to file in the control folder, so the component may be stopped and restarted with failed attempts continuing. The EML spool files are compatible with those created by many Microsoft email applications such as CDO, and the AddtoQueue method can also be used to queue existing EML files with the queue details specified in MailQuItem. Note, this component is intended for sending low volume email from individual Delphi applications, with more flexibility than a simple TSslSmtpCli component. For use as a heavy duty SMTP server, queue processing could be improved to avoid moving records around as much or saving them to disk as often, and mail bodies could be read as required from disk instead of being read entirely to memory first. DNS look-up could be added to find the MX records for each domain to send email directly. A mail pickup folder could be added which is scanned for new EML files. Finally, an SMTP server component could be added to accept new email on port 25, and save it as EML files for redelivery. Beware such an addition has various security implications for open relaying and spam detection. Angus -- To unsubscribe or change your settings for TWSocket mailing list please goto http://lists.elists.org/cgi-bin/mailman/listinfo/twsocket Visit our website at http://www.overbyte.be
