I sent an email to a mailing list of 650 people. Usually it has always worked but this time it stuck on 20 mails. So I updated WordPress and Mailpress in their latest versions. The shipment took over and it is blocked again in 60 emails.
- I checked the logs but it is not very meaningful. (http://www.sendspace.com/file/of6zw2)
- I checked that my host does not block sending emails.
- I checked the permissions of the tmp folder (705).
I do not know what else to do.
Thank you for your help,