Plesk has a built-in limit of 4 concurrent connections to IMAP from a single IP, so if you have more than 4 users – or more than 4 accounts which connect back to your Plesk server from any 1 IP – your users will get a Send/Receive error.
![](https://www.mikcx.com/wp-content/uploads/2011/11/pic-plesk.jpg)
Plesk has a built-in limit of 4 concurrent connections to IMAP from a single IP, so if you have more than 4 users – or more than 4 accounts which connect back to your Plesk server from any 1 IP – your users will get a Send/Receive error.