Bearing in mind I haven't yet done any benchmarks, which do you think is faster - SMTP with multiple RCPT commands or the PHP mail() function (with it launching a separate sendmail process for each mail() function call)?
No brainer, SMTP will almost certainly be faster. My mailing list system (written in PHP obviously) can dump 600k customised emails to the local SMTP server in a couple of hours. Doing the same with the mail command took over 24 hours. How much slower will depend a lot on how you have configured sendmail, but it's never going to be faster than a socket connection to the local SMTP server.
Thanks.
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Richard Heyes
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