problems sending to prodigy.net hosted email

[list at satchell.net (Stephen Satchell)]

On 03/17/2018 02:04 PM, Chris wrote:
> Stephen Satchell wrote:
> 
>> (I know in my consulting practice I strongly discourage having ANY
>> other significant services on DNS servers.  RADIUS and DHCP, ok, but
>> not mail or web.  For CPanel and PLESK web boxes, have the NS records
>> point to a pair of DNS-dedicated servers, and sync the zone files
>> with the ones on the Web boxes.)
> Why not? Never had a problem with multiple services on linux, in
> contrast to windows where every service requires its own box (or at
> least vm).

1.  Spreading the attack surface across multiple system.  Just because 
someone is nailing your web server doesn't affect your DNS server, or 
mail, or authentication, or logging, or...

2.  Robustness during maintenance.  Browsers cache DNS responses, 
including NXDOMAIN responses.  Just because your web server is 
inaccessible while you do something with it doesn't mean the browser is 
completely disconnect when you bring it back up.  Ditto mail servers

3.  Application-specifc attack mitigation on each type of server.  It's 
far easier to lock down a DNS server if you don't have any other 
significant servers running.  Ditto for mail, ditto for Web, ditto for 
syslog servers, and so forth.

4.  Limit what an attacker can do if s/he "breaks through" your 
protections.  I even go so far as to impose severe limits on the 
internet, nominally "trusted" network, to minimize cross-server attacks 
through the local network.  In short, systems should *not* blindly trust 
neighboring systems.

I don't like publicly facing VMs.  They are find for internal functions 
that are *not* exposed to the world.  (You can't help it with 
cloud-hosted objects, but just remember that cloud servers can be 
compromised just as easily as iron-hosted servers, perhaps even more 
easily.)

About cloud:  I prefer that any cloud-hosted servers not have 
mission-critical functions.  The best use of cloud servers, in my 
opinion, is to host user interface tasks, and tunnel through to servers 
in my machine room for data.  Depends on the application, but my 
critical data is in my machines.

I still recall when I was working on APRAnet and the Morris worm first 
launched.  I also recall when the IMPs were flipping bits so that 
packets would have addresses changed and start running forever until the 
entire ARPAnet was restarted.  That's when TTL was introduced into the 
NCP implementation at the time.