A sendmail and mailing list question

[m.roth2006 at rcn.com]

We're having an issue at work: the corporate mailserver's gone from a propriatary package to sendmail. The propriatary one allegedly did not verify addresses before sending, while sendmail, at least in the configuration they're using, does. One team of users (production) sends out an alert to subscribers, which can be many hundreds, and conceivably over a thousand, emails. We batch them in groups of 100, so as not to be handled as spam by the filters. However, what we're seeing is failing after 4 or 5 min, RSET by a timeout.

This *can't* be right. This list is surely running on sendmail, and I'd be very surprised if there were less than a 1000 subscribers to this list, yet a posting is out in minutes.

Anyone have any ideas? One guy at work was wondering if they are not caching domains (it does seem to be verifying each and every address).

    mark