You could use the DIGEST feature to put all messages for a single day into a single e-mail message. Also filters/rules for separate mailboxes helps.
Another possibility for checking if there is a new posting at all is a program that checks for changes to a website. For a Mac, the Simon program from Dejal does that among other monitoring tasks. I found this link for some other solutions that do the same kind of thing:
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www.ghacks.net]
One can even script monitoring websites for changes with wget, diff and a crontab entry.