code 421 4.4.2 Message submission rate for this client has configure the configured limit

Hi guys,

wondering if anyone can enlighten me on this error:

Expected response code 250 but got code "421", with message "421 4.4.2 Message submission rate for this client has exceeded the configured limit

A staff gets this whenever he wants to bulk update (close) tickets.

Was of the opinion there was a limit on the mail account used by kayako however, the ms exchange guy says there's no limit.

I've checked under settings>Email settings to find where i might increase this "message...

code 421 4.4.2 Message submission rate for this client has configure the configured limit