Catchall e-mail addresses are mailboxes that receive messages for a domain that do not match any specific address in that domain.
For instance, if someone sent an e-mail to email@example.com when no such e-mail address existed, it would get routed to a catch-all address for the exampledomain.com domain.
If no catch-all address was set up, it would simply be bounced back to the sender with an error.
For a long time, catch-all addresses were immensely useful. When e-mail was still relatively new, a domain could use a catch-all address to make sure e-mail with a slightly misspelled mailbox name could still make it to the intended recipient.
Upside of Catchall Email Accounts
Some of our customers making use of a catch-all find that they don't need to set up any separate email boxes. Instead, they simply use the single catch-all email account and can therefore give out any email address at their domain that they like, any time. Even if somebody misspells the name part of their email address, they'll still receive the mail.
The Downside of Catchall Email Accounts
One unfortunate downside to the catch-all account is that with the increased levels of SPAM (unsolicited) email circulating on the internet, the catch-all mailbox also catches the many spam emails that are targeted to random addresses - for example "firstname.lastname@example.org".
Secondly, if you were perhaps unaware of the catch-all mailbox, or simply forgot to check and clear it, it can very quickly fill with SPAM. Because the catch-all is only limited by the size of your account, it is possible to use your entire hosting account disk space allowance with this single mailbox.
When your account fills, no further email can be delivered to any of your mailboxes until space is cleared again.