[CentOS] Re: Mail server setup for small ISP

Matt wrote:
>>        I will probably have to design an e-mail (and other components)
>> infrastructure for a small ISP soon (WISP).
>>
>>        I'm doing some research to determine which components would be best to
>> offer e-mail services to their client and allow the staff to manage
>> accounts easily.
>>
>>        I usually use virtual machines a lot for isolation and easy backups and
>> migration (when a hardware node is underpowered, it is easy to migrate
>> one or more virtual machines to another hardware node easily).
>>
>>        I have looked at iSCSI and drbd for high-availability of the storage:
>> http://www.pcpro.co.uk/realworld/82284/san-on-the-cheap/page1.html.
>>
>> This looks like it should be doing a great job of high availability storage.
>>
>>        For mail server, I guess I should look at an MTA and IMAP/POP server
>> that supports LDAP and/or MySQL for users.  Postfix should be a good
>> choice for MTA, as I know it (at least a little, but I know sendmail
>> better).  For IMAP/POP, I'm not sure...  Would dovecot be sufficient, or
>> should I try cyrus.  I'd rather use components that are available for
>> base or extras repository (or rpmforge).  I think that squirrelmail and
>> horde would do a good job for webmail.
>>
>>        There shoudn't be any troubles having some redundancy for DNS, web
>> servers, mtas, but what about IMAP/POP? linux-HA?  MySQL replication
>> should be enough, I guess.  Or maybe linux-HA as well.  I wonder if I
>> should add GFS to the mix to have multiple IMAP/POP servers use the same
>> storage.  Or maybe IMAP proxies?
>>
>>        Any insights welcome :).
> 
> www.directadmin.com
> 
> Been running it on CentOS for years.  Added Clamav and spamassassin to
> it.  It utilizes Exim and dovecot along with standard bind and apache
> stuff.  You pay monthly or yearly license fee.  Its pretty cheap
> really.  You can also pay a one time fee for a given machine.
> 

Thanks

Does it offer some kind of high availability features?  Does it provides 
an API (for account creation/management from another system)?