how to limit number of simultaneous outgoing smtp connections ?

[alopeza]

hi all !

we have a production server dedicated to deliver emails for a distance learning platform used by thousands of attendants.

when the forum posts are distributed by email, the zimbra mail server tries to deliver all emails as soon as possible, the communication link gets saturated, many tries timeout, making the situation worse and worse.

we would like to configure zimbra to get out emails at an slower pace; we don´t mind if the mailing process takes longer, what we want is to optimize the bandwidth usage with succesfull sends rather with fast timeouts.

how could this be done ?

thanks again,
Antonio