On Jun 9, 2010, at 6:38 PM, Joey Kelly wrote:
> I get several errors, but the most obvious one is that I'm sending to too many
> recipients at one time.
Are they rejecting your mail or just throttling you?
If this is a new IP address from which you're sending, they need to first build up some reputation of whether those mails are wanted by their customers. Over time, the mail will go through. What you may have to do is configure postfix to trickle the mail out to these places, say by limiting it to 1 concurrent connection per destination domain.
You do this by setting a transport map to map "yahoo.com" to the transport "trickle". Then in master.cf you create a copy of the "smtp" line and change "smtp" to "trickle", and then in main.cf you set "trickle_destination_concurrency_limit = 1". The postfix list will provide more help if you need it.
Once yahoo/aol/gmail/hotmail get used to your IP, you can bump up the concurrency until ultimately you don't need the throttle anymore.
That and using DKIM is a great idea. Just be sure to strip any DKIM on the incoming messages first so as not to confuse the remote verifiers.
Your other option is to use a list hosting service who has taken care of all the ISP relations for you.