I am a long term Gmail Apps user and use catch-all behaviour in my Gmail account. I have only 1 email address connected and get about 600 spam messages per 30 days, nearly 100% of which are marked as spam automatically. Therefore they don't interfere with the operation of my Inbox.
I also publsih my email address on the Internet widely - social media, mailing lists, forum, live blogging etc and this has not affected the amount of spam at all.
I am also subscribed to a huge amount of notification services and mailing lists, causing maybe around 6000 emails to hit my email and be filed automatically
My first name is German and very unusual for an English speaker - I explain in a moment why I think this may be important.
I use the web interface and "Report Spam" systematically.
I have a client on Gmail apps. They have a brick and mortar business with 12 email addresses and catch-all turned on as well - because Gmail doesn't support mail aliases.
The catch-all account doesn't have the mailing lists and notification services subscribed, but receives around 52000 spam in 30 days.
The client is not throwing his email address around as I am and the few "commercial unrelated" email pieces he receives are from other brick&mortar businesses that he probably has frequented at least once.
However the client has a very common English first name as his email address.
The spam he receives is about 60% bounce notification, ie. caused by the domain name being used as a sender, however rarely does it actually use a common English first name, it is always a random text. About 100 messages per day make it into the Inbox.
The client uses Outlook, so they do not report Spam to Gmail.
Knowing some basic spam filtering techniques, the above comparison is counter-intuitive to me. Is the difference really all down to spam reporting?
A shortcut way to solve this will be to set up a filter that archives all mail that is not addressed to the person or the aliases. Mid term I hope "reporting spam" will solve the problem.
Any other comments anyone can make?