[RFCI-Discuss] DNS record's TTL requirement?

[Matus UHLAR - fantomas]

On 07.07.06 10:34, Jeff Pang wrote:
> Sorbs said on their homepage:
> 
> * The MX record of a domain needs to contain a host name that maps to the
>   IP address involved. The Time to Live of the MX record needs to be at
>   least 43200 seconds.
> * The A record for the host name needs to have a TTL of at least 43200
>   seconds.
> * The reverse DNS PTR record for the IP address involved needs to map back
>   to the name given in the MX record, and to have a TTL of at least 43200
>   seconds.
> * If there are multiple MX entries, these rules apply to them all.
> 
> Why the DNS records' TTL should be more than 43200?Is there any RFC
> about that?

No, SORBS is just a bit paranoid about people putting temporary low-TTL MX/A
records onto hosts/domains when they want SORBS to delist them.

> (When the TTLs for some hosts' A record or ptr record are less than
> 43200,Sorbs should consider these hosts' IPs as dynamic IPs.)

No wonder. Some people (mostly spammers) can do whatever to get they mail
delivered even if there are good reasons not to accept them (e.g. servers
that refuse mail from non-local dynamic IPs).

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