I will modify the DNSBL plugin, so that it will be possible to prepend the required access key before the reversed IP. That's not a big thing. Remind me, if it is not available in next myroundcube plugins bundle release.
Thanks !! See, I'm not a PHP coder, but I thought at that; I mean, I tried to figure out how to add a syntax like foobar.$IP.somebldomain.ext so that the $IP if present would be expanded to contain the reversed IP address (while if not present, the regular BL lookup approach would be used)... but after scratching my head for a while I wasn't able to figure out how to do that, so... THANKS !
Had a further look at the code for your dnsbl plugin; so... well, allow me to post a couple notes; first of all, it sounds like it's spawning "nslookup" to run checks against each DNSBL, now, not that it's bad, but since PHP seems to have its own built-in DNS lookup functions Using PHP to Perform DNS Lookups :: v-nessa.net :: Programming is Sexy
and since the overhead of using them (and call directly the OS libraries) is lower than the one from a "spawn", I think changing the code to leverage such calls may be a good idea; next, and since we're at it, the default config for the plugin, carries some DNSBLs which may be perfectly ok in case you want to filter incoming SMTP hosts but which aren't so effective when it comes to webmail "rattlers", so, I'd suggest changing the default lists as follows
/* Services to check */
$rcmail_config['dnsblacklists'] = array(
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