Re: Strange mail problem

Also, if you just installed a new debian system, the default MTA is exim4.
Try typing "dpkg -l |grep exim", do you see any exim packages listed?

https://wiki.debian.org/PkgExim4UserFAQ says exim delivers the first
10 messages and puts the rest in the queue.  It suggests making fetchmail
run "exim -q" in the postconnect, or just use procmail to bypass your local
MTA.  Just for completeness, https://wiki.debian.org/Exim also exists.

The exim option smtp_accept_queue_per_connection default value is 10

from http://www.exim.org/exim-html-current/doc/html/spec_html/ch-main_configuration.html
This option limits the number of delivery processes that Exim starts automatically when receiving messages via SMTP, whether via the daemon or by the use of -bs or -bS. If the value of the option is greater than zero, and the number of messages received in a single SMTP session exceeds this number, subsequent messages are placed on the queue, but no delivery processes are started. This helps to limit the number of Exim processes when a server restarts after downtime and there is a lot of mail waiting for it on other systems. On large systems, the default should probably be increased, and on dial-in client systems it should probably be set to zero (that is, disabled).

original source: https://stackoverflow.com/questions/3914357/problem-with-sending-multiple-mails-per-smtp-connection-with-zend-mail-and-exim/5193004