Now I'm writing a software to send to big C posters and i wonder what's the max per "from:" you could send per day or per time period. Have anyone tried it? How many u could send per day or hour?

All the time you wasted asking that question you could have searched.

yes this is one forum that the search feature works great.

I did search it but most people says it's around 20 per hour.. is that true? i tested and haven't got any bounce yet. Will it bounce like regular email or special message from them.?

If you had "gotten off your ass" and tried you would find that craigslist only allows 20 emails per sender.

Why would they bounce, they will just drop them.

I have done 250 plus in three hours twice before. The first time about 33% were flagged, the second time all of them were ghosted. The good thing is I now know why, after hours of reseach.

I'm still learning with CL but from what I have learned so far I can't see why posting would be limited to 20 per hour, the ghosting and flagging depends on multiple variables such as IP address, uniqueness of post, 'spamminess' of post, catchall or account, urls in post, time lapse between posts, city, ad section etc.

I would say that if you have all of the above conquered, and you have the facility to rotate them all between posts, then there is little or no restriction.

And from experience, I would advise that your software needs to be flexible enough to provide the facilty to rotate all of the variables.

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Did you read the OP?
He's asking about sending EMAIL to *@craigslist , the address they setup for posters to receive messages.. He's not asking about posting limits.