The wiki has this to say about the email limit;
[color=#0000CC]"Websites that send email are limited to 100/hr via SMTP and 200/hr via SSH/SHELL."[/color]
DreamHost have said that they are willing to vary this limit on a case-by-case basis, given a good enough reason, but as mao said; The DreamHost provided mailing list is not subject to the limitation, so it's a good idea to use this if possible.
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