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Catch-All Email – Spam with a sprinkling of ham

What is catch-all and what was it good for?

Catch-all could also be called wild-card email, in that a catch-all mailbox allows for an email sent to any username under a domain to be delivered to a single mailbox without having to define a valid username. With us so far?

This is probably best shown by example:

Imagine we have the domain name ‘mycompany.com’ and mycompany has four employees Andrew, Bob, Carl and David with Andrew being the company owner leaving Bob, Carl and David as employees.

Andrew being the boss wants his employees to have their own mailboxes and creates a mailbox for bob@mycompany.com, carl@mycompany.com and david@mycompany.com in addition to his own andrew@mycompany.com.

Now Andrew also wants to give his customers some generic email addresses so that they can contact sales@, info@, support@ etc, without knowing the specific person responsible for each department and have those emails come through to andrew@ for redistribution/forwarding to his team.

Traditionally, Andrew would be entirely correct if he enabled a catch-all on the andrew@mycompany.com mailbox, meaning that if an email was sent to anything except bob@, carl@ david@ it would then go to andrew@.

So what is wrong with catch-all email and why is it not so good?

As you might expect whenever discussing anything to do with email, we come back to the subject of spam and as per the title a sprinkling of ham.

Let us illustrate this example with some statistics from a customer’s domain:

The customer’s domain in question has been around for 12 years, is the company name and primary email domain for their many employees over the years but for the past couple of years is now home to four employees and their mailboxes. Lets call these first.name@ second.name@ third.name@ and fourth.name@ and they have three other email addresses in use info@ sales@ and support@ and lets call the domain name acompany.com

How many emails per month are sent specifically to the employees/company?
~ 1500 first.name@acompany.com (including info@, support@ sales@)
~ 1200 second.name@acompany.com
~ 1100 third.name@acompany.com
~ 1100 fourth.name@acompany.com
~ 4900 Total

How many emails per month are sent to other invalid or random email addresses which don’t exist?
~ 200,000

This means that the mail servers needlessly accept, scan for spam/anti-virus and potentially deliver to the catch-all mailbox 195,000 unwanted emails. The majority of these emails being sent to random@ and other guessed email addresses that the spammers use to try and get their message in front of you and your staff.

Even if the anti-spam and virus scanning was 99% effective, that would mean 1950 unwanted emails per month needlessly received in the catch-all mailbox.

Counting the cost of these emails, if takes you just 3 seconds to read and delete each of 1950 emails that’s 97.5 minutes per month that you could be spending on your business or enjoying away from your email client. That’s before you consider the electrical power and bandwidth involved in needlessly processing/crunching/scanning 195000 emails per month.

So what can be done about it?

We highly recommend that you disable catch all and instead take a good look at all email addresses in use under your domain(s) and use mail aliases for email addresses you want to receive email on, but do not wish to create a mailbox for.

Using the above example domain this would look something like:

first.name@acompany.com – mailbox
info@acompany.com – alias to first.name@
sales@acompany.com – alias to first.name@
second.name@acompany.com – mailbox
third.name@acompany.com – mailbox
support@acompany.com – alias to first.name@ and second.name@ and third.name@

This will ensure the delivery of valid emails to the relevant parties and avoid the needless scanning of misaddressed or otherwise spam email.

If you’d like further advice on how to most efficiently configure email for your domain or business needs, please contact the support team through the usual methods.

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Classification: Public
Last saved: 2021/11/11 at 14:18 by Jamie