Hi On Wed, Oct 30, 2013 at 09:26:56AM -0400, Roman Gelfand wrote: > Looking at the tcp stream, below, of a smtp conversation, it appears > there is 5 second delay before the actual smtp conversation begins. > Is this normal behavior. If not, any ideas what/where specifically, > in networking, I should be troubleshooting? No change was done to the > server or any other machines on the network. This started happening > all of a sudden.
There are a couple of possibilities for this delay. Some mail server (exim4 for example, I believe) introduce a small delay before sending the SMTP greeting. SMTP clients are *meant to* wait for the greeting before sending SMTP commands, but (apparantly) many spambots did not. Thus, rejecting email where the SMTP client was "too eager" turned out to be a decent way of reducing spam. I suspect that spammers have not learned to obey that standard, so it may have little effect. Another possibility is that the mail server attempts to do a reverse DNS lookup on the source of the connection - but this will usually be a longer delay Hope this helps -- Karl E. Jorgensen -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20131030133301.GA13800@hawking
