[Linux-cluster] Postfix active/active mail cluster

[Gordan Bobic]

Mehmet CELIK wrote:
> 
> Hi, of course, you can do this. so, each node on *LVS will respond 
> active.

Not much point - DNS load balancing works just fine for a mail server. 
Or you can use the cluser resource manager to migrate the IP of a downed 
node to another node.

> But, this is different from storage subject. The IMAP don't be 
> problem. But, the SMTP can be a problem. Because, you have dynamic ip on 
> the RBL checks. For this, you must use smtp gateway. All outgoing smtp 
> traffic must be from a single IP.

I don't remember anyone saying that dynamic IPs are used. Just because 
the mail cluster has a different IP for each host doesn't make them 
dynamic. RBLs that block dynamic IPs largely only block 
dial-up/broadband dynamic IP ranges, and I don't thing the original 
poster ever suggested that this is the sort of range the mail cluster 
he's building will be on.

There is no RFC that states that all mail from a domain must come from 
one IP. Having multi-homed mail servers with multiple IPs is perfectly 
RFC compliant. Google do it, for example, as do many other mail service 
providers. The main issue with this is that there are people who use 
fundamentally broken anti-spam measures like greylisting, which fall 
over flat on their face when consecutive delivery attempts come from 
different IPs. Breaking your mail cluster scalability to work around 
someone's broken mail system is, IMO, not the correct solution.

However, as I mentioned in the other post on this thread, if you make 
the mail spool local rather than shared, then the outgoing mail will not 
bounce between the nodes - it will remain on the same node until 
successfully delivered (or bounced). This works around the problem of 
broken mail systems.

Gordan