Issue 503 when receiving large volume of mail in a short time

[joseceta]

Hi, I have a problem, I have a plesk that has a domain with 800 email accounts and we have observed that the days that a massive mailing is done to those 800 accounts the server stays "dead", gives 503 the email does not work for a few minutes .. may it be dovecot configuration that has to expand the memory allocation? it's a vps but at no time do we put the server's memory to the limit.