I am helping my friends sending a newsletter (1000 recipients) using Thunderbird 7.0.1 and the Mail Merge plugin.
For the SMTP provider we are using Sendgrid.
Mail Merge plugin nicely splits the messages into individual ones and starts sending them, but they are having timeout problems with the SMTP server.
Do you have any idea why is this happening? Is Thunderbird trying to send all the mails in it's outbox at once? I hope it is not the case. Is there any way to control how is Thunderbird processing it's queue? Is there any plugin for Thunderbird to control this behaviour?