Sendmail and backup MX

[Steve Campbell]

Well, I guess I misinterpretted the question. I thought he meant "simple 
solutions for sendmail that only lets the
backup MX accept mail when the primary is down?" and not anytime such as 
when the primary is up.

BTW, Denis, when you send "certified" mail, it makes it very difficult to 
reply to your message.

Thanks all for correcting me. I stand corrected.

Steve Campbell
campbell at cnpapers.com
Charleston Newspapers


----- Original Message ----- 
From: "Kevin Miller" <Kevin_Miller at CI.JUNEAU.AK.US>
To: <MAILSCANNER at JISCMAIL.AC.UK>
Sent: Monday, September 26, 2005 3:55 PM
Subject: Re: [MAILSCANNER] Sendmail and backup MX


> Steve Campbell wrote:
>> I believe DNS does this if you have your secondary MX defined in DNS
>> with equal or lower priority than the primary.
>>
>> The primary will not accept mail as it's down.
>> DNS will direct mail to the secondary automatically.
>>
>> I think this is all proper. I could be wrong though.
>
> Yes, that's right more or less.  Except that in practice the primary 
> doesn't
> have to be down - if it's up but momentarily busy the sender may fail over
> to the secondary.  Also, many spammers target the lower priority servers, 
> on
> the assumption that they're less likely to be updated w/the latest 
> greatest
> spam filters.  I have a terciery server that sees maybe a dozen real mails 
> a
> day, and several hundred high scoring spams.  I'm quite content to let it
> vaporize spam and send nary a real message - takes the load off my other
> mail servers.
>
> Don't have any examples for the OP, but I'd venture that a script in cron
> that checks for port 25 on the primary should be pretty easy.  If it 
> fails,
> have it kick off sendmail on the 2ndary.  There's a number of status
> checkers out there...
>
> ...Kevin
> -- 
> Kevin Miller                Registered Linux User No: 307357
> CBJ MIS Dept.               Network Systems Admin., Mail Admin.
> 155 South Seward Street     ph: (907) 586-0242
> Juneau, Alaska 99801        fax: (907 586-4500
>
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