Bullet Proof MX setting for a domains

[thok]

I use a personal email address ([e-mail]) for most of the times and this domain is connected to every thing important like bank accounts and credit cards.

Currently this domain is hosted at hostgator.com
And I am using google apps with this domain (so my email is actually over the gmail for custom domains).

For this I have set the MX records to direct mails to Google in the cPanel offered by the hosting provider.

Now about the real question, What happens if the host went down for extended time ? And what if they mistakenly cancel my account ? Or some disaster happen at their datacenter and all their servers go offline? What will happen to my email ? I guess it wont work any more ? Right?

So I want t fool proof system .. I want to set backup of this MX entry and want to make sure that any problem with hosting service doesnot effect my email settings ? Can any one help me with this ? Any ideas?

[lammert]

In your current setup, the DNS server of your hosting company is the only service of your hosting company which is used to deliver email and whose malfunctioning may cause havoc. If that server goes down, sending SMTP servers will receive a timeout when trying to retrieve the MX or A records for example.com.

The SMTP protocol allows server outages and defines a retry mechanism. According to RFC5321 [ietf.org]:

The sender MUST delay retrying a particular destination after one attempt has failed. In general, the retry interval SHOULD be at least 30 minutes; however, more sophisticated and variable strategies will be beneficial when the SMTP client can determine the reason for non-delivery.

Retries continue until the message is transmitted or the sender gives up; the give-up time generally needs to be at least 4-5 days.

If something goes wrong at your hosting company side, you have at least four to five days before emails queued for delivery to your email server are marked as undeliverable. 4 to 5 days should be enough in most situations to solve the problems. If you are looking for a more bullet proof setup, you could look at specialized DNS service companies which are specialized in delivering DNS services with 100% uptime.