“imap” service reaches its memory limit

This morning I received this email from our CPANEL facility: When the "imap" service reaches its memory limit, the system performance will suffer because the service must start a new process and it will lose all of the data that it has cached in memory. You should increase the current memory limit of "2 GB" or remove any unwanted email from the (hides account for sensitive data) account. To increase the memory limit, use the "Maximum Size of a Mail Process" setting in the "Mailserver Configuration" interface in WHM. The command that they indicate to me to execute I changed this service to 4GB. I want to know what all this affects because I can't find anything through your Forum or Google. Just indicate that they are accounts with unlimited size. Is that size not compatible with the correct operation of CPANEL? Thanks.