[Dovecot] How to limit max number of connections for ip address

[Timo Sirainen]

On 24.2.2012, at 17.07, Wilberth Perez wrote:

> My question was because constantly we received brute force attack from
> some of ip address which uses pop3 service to affect dovecot's login
> proccess.
> 
> For example:
> 
> dovecot: Error: pipe() failed: Too many open files
> dovecot: Error: Temporary failure in creating login processes, slowing
> down for now

This is your main problem. Increase ulimit -n so Dovecot won't stop creating login processes (or alternatively decrease the max number of login processes). Newer Dovecot versions warn at startup if the fd limit is too low.