'Hacking' as the legitimate, code-loving way, that is ;-)

I have a weekly newsletter and I want to send several messages. Each recipient has a slightly different letter with a unique "unsubscribe" URL.

I don't want to use the transport relay of an MTA like postfix. I want to code it myself and access directly my ISP's SMTP server.

Is it (possible / legal / moral) to use a single connection to send all these copies or should I use multiple delayed (1 or 2 seconds) connections for each letter ? I don't know which is better for testing my ISP's good-will and patience ;-)

Any hint appeciated.

I would think the multiple delayed connections would be better personally... But it depends on your ISP's "Acceptable Use" policy.

Why don't you want to setup and use your own MTA? The data has to leave your PC anyway, wouldn't it be better and less "infringing", to send them directly from your network to the recipients server and leave your ISP's mail server out of it?

You should use just one connection.

Dont do multiple connections as the same time, you probably will be blocked!

[]´s, FMC!