I'm using the Smart Mailer component, trying to send newsletters from a database to aprox. 600 receivers.
The component is sending to 40-50 receivers, and than stops

The error I get is:

SendMail Error: [10054] Connection reset by peer


This error means that the mail server is shutting down your connection to prevent spam.
This happens often this days when people try to send bulk mails at once to a single mail server. It is a standard technique called Grey Listing - the mail server denies your mail for a while.

You can solve this by not sending all mail to your specific server directly but by using the ASPEmail Queue.

There is an option in the Server Settings tab called "Use Queue To Send Mail"

When enabled the mail is send not directly to your mail server, but placed in a queue and then send one by one by the ASPEmail Mailer service. If then an error occurs the services simple retries so you mail is eventually send.

Just make sure that your provider have enabled the ASPEmail Mailer service and it is running.