On Mon, 20 Mar 2006 10:30:35 -0400, Bruno Robichaud said: > Thx for the tips, About the Mail transport agent right now we using the IIS > SMTP, which other SMTP would be more efficient than this one. I'm not aware of anybody who is doing a million e-mails per day using the IIS SMTP. On the other hand, doing a million e-mails per day using Sendmail on a Unix/Linux box is no trouble at all once you spend some time tuning it, an a million per hour is achievable with some work. 10M per hour will involve some investment in serious hardware resources, however... ;) General hints that will apply no matter *what* MTA you use: 1) Get a good handle on what SLA you're expected to meet, and make sure it's physically possible. Delivering 95% of a million e-mails in the first 6 hours is no trouble at all. Delivering 95% inside 15 minutes is a challenge. And if they want 100% delivery in *any* timeframe, point out that there is no way you'll get a million addresses that exist and are reachable - servers at the other end will be down, backhoes will pop underground fiber bundles while doing their mating dance and demonstrating their digging prowess (Spring *is* the traditional backhoe mating season, you know). 2) Although the RFCs frown on it, you're best off making *one* attempt to deliver the mail with drastically shortened timeouts. One particularly big win is to timeout the *initial* connection attempt after only 5 seconds or so ("O Timeout.iconnect=5s" for Sendmail's .cf file) - if they can't get a TCP 3-packet handshake done in 5 seconds, they're probably down. After the first attempt, *get them out of the way* and re-try them with more traditional timeouts later. 3) If most of the mailings are going to the same people as the last time, I *highly* recommend a local caching-only DNS server - if you have enough memory, running it on the same machine as the MTA is ideal. The round-trip time to look up MX and A records can be a *major* throughput killer (eliminating *one* particularly badly timed MX lookup in Sendmail resulted in a 6X speedup on my Listserv box. 'FEATURE(nocanonify)' in the sendmail.mc file is the magic incantation). 4) Make sure all the 'User Unknown' bounces get fed back for removal from the database. 5) Be prepared to have somebody watching the queues in case some site you send a lot of mail to goes belly up. If 1% of your subscribers have yahoo.com addresses, you will almost certainly end up with lots of mail queued for the yahoo.com mailservers (1% of a million means 10K recipients headed there, which will irritate their mailservers and generate lots of '421' errors). 6) If you don't have a clue what an SMTP 421 error is, find somebody who does. If you're sending a million pieces of mail a day, you *will* need somebody who's technically skilled to deal with sites that think you're spamming them, or sites that block you because they don't like technical incompetence. 7) Have working *and responsive* abuse@ and postmaster@ aliases. Failure to do is one of the quickest ways into many places' blacklists. See (6) above....