[tlug] Overloaded mail spool causing memory instability?

[Dave M G <dave@example.com>]

TLUG,

In the last month or more, I've been having a fair amount of email 
instability on the web hosting service where I have a virtual private 
server (VPS) account. Every now and again, my POP and SMTP (Exim?) 
server would have to be restarted.

As I'm sure we all experience with computers, when things go wrong, you 
sometimes find that there is more than one problem at work, and all the 
problems together tend to make it hard to pull them apart. Nonetheless, 
with some help from this list, I've been putting out the relevant fires.

Most recently, it was brought to my attention that all unrouted email 
sent to the domains I own were being routed to the default mail account 
for that domain name. This meant that as spammers experimented with 
different email addresses on my domains, they would all be recieved, and 
the spammer would think they have a positive result, and so most likely 
continue to send email to that address.

I shut down the mail routing, but my email was still a little unstable. 
Then, to clean things up, I went and looked in the inbox for the default 
mail account for each domain to see how much spam was in there.

Most domains had about a thousand spam emails, dating back to about a 
year when I first opened my VPS account with my current web host. That 
number of emails didn't strike me as anything special.

However, it turned out that one account had a whopping 60,000 emails 
sitting in there. It took forever to simply delete them all.

It got me thinking... would an overloaded email inbox on a server 
potentially affect memory usage? In the sense that each email coming in 
presumably has to be processes somehow, and if it has to be placed at 
the end of a large spool file or something, perhaps that large spool 
file would have to be read or loaded or something. If that spool file 
were ridiculously huge, might that soak up memory and cause possible 
time outs or max out available resources?

What do you guys think? Can 60,000+, and constantly growing, emails in a 
server inbox choke the resources somehow?

--
Dave M G
http://www.tlug.jp/wiki/User:Dave_M_G