LDAP Accept Query or SMTP Call-Ahead

[ArjanBroekhuizen]

Hello all,

We have configured LDAP Accept Queries for checking incoming mail for excisting SMTP-addresses. This is with a VPN from Cisco to our server.
I heard about the option SMTP Call-ahead, which has the same function. What is the difference between both functions and which one is better?

Kind regards,
Arjan

[Ken Stieers · Accepted solution]

Ldap accept is better.

Smtp call ahead creates more load.

Smtp call ahead starts sending a messge to your mail server and aborts it if your mailserver doesn't like the TO header.

I don’t knownif it caches that result , but LDAP does have a cache. Also LDAP lets you do things like group checking, spam quarantine consolidation, mail routiing, etc.

[ArjanBroekhuizen]

Hello Ken,

Thanks for your reply. Good to hear that we already have configured the best option
The thing is that we use a VPN-connenction for LDAP. When the VPN is down, we don't have LDAP-checks and mails are dropped. I thought SMTP Call Ahead could be an solution for that, but apparently it isn't.

[Ken Stieers]

Check the ldap cache age. You might be able to bump it up so you don't see as much dropped mail? There's a balance there of course...

[ArjanBroekhuizen]

Hello Ken,

Thanks.
Where can I find the cache configuration? I don't see it in the server profile (System Administration, LDAP, <server profile>) or in the Global LDAP Settings (System Administration, LDAP, Edit Setting).
Under the Global Settings, there is an option Flush Cache, but this isn't a configuration option.

[Ken Stieers · Accepted solution]

Click on the "Server Profile" where you set the hostnames/ips/etc, then click on Advanced, and you can set the cache settings there. 

[ArjanBroekhuizen]

Found it. I see that the standard cache TTL is 15 minutes. That should be enough for minor connection interuptions.

Thanks for your help with this case!