Mohsen Masoudfar writes:
I created a new list with this setting. This new created list can send to Gmail addresses, this is very strange, because I have changed the problem list (The list that cannot send to @gmail addresses) settings to match the new one, but still the issue is there.
The problem may also be that Google has decided that your existing list has a bad reputation, that is, it had too many posts rejected in the past. The new list doesn't have that problem.
The problem that mailing lists face with the biggest email providers is that they don't have acceptance policies any more because they use algorithmic reputation engines. *They* don't know why your email was rejected. (Truth be told, none of us do since we use Bayesian spam filters. But at least if you use SpamBayes you know what features are being evaluated. Machine learning algorithms use "features" that are too tiny to be connected to spam except with big data.)