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I keep running out of memory every now and again. What's happening?

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If you're using spamassassin to filter all mail on your domain, you will run out of memory, unless you impose a limit on simultaneous scans.

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Finally, if you are using an MTA like Postfix that allows control over how many concurrent local deliveries to allow, set that to a sane number; for example, Postfix allows you to specify a limit of 5 local deliveries at once by adding this line to "main.cf":

No Format
local_destination_concurrency_limit = 5

This helps throttle down the load further upstream, and is very beneficial.

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