To whomever might help,
Problem: I'm having many many emails that log as dsn=2.0.0, stat=Sent (Ok: queued as CA29A4FC7D) or dsn=2.0.0, stat=Sent ( <21431207.1095024967457.JavaMail.root@mail.ceocast.com> Queued mail for delivery) for Hotmail emails, but they never get delivered.
Relevant Facts:
- Sendmail 8.12 on Linux. Java creates the messages and sends them to sendmail. The box has 2 new Xeon procs and 2 gigs of RAM.
- A nightly email sends out and is delivered successfully to all legitimate addresses. Sends about 8,000 text only emails. I'm a little Linux ignorant, but I use "dir | wc -l" to get a file count in the queue (var/spool/mqueue) which reads about 220 at the height of the nightly run.
- The problem run occurs once a week on weekends, and sends out approx. 80,000 emails. The messages are multipart, half text and half HTML, and each weigh about 50k. I took a count as above in the queue, and it peeked around 1,590.
- AOL(once I got on their whitelist), Yahoo, Comcast and other fast ISPs get delivered to ok on the weekend.
- I sort by filename, and sort the mail in Java before it's delivered to Sendmail by email address (NOT by host).
- I mention fast ISPs, because I noticed that with at least on smaller domain, the addresses early in the alphabet go through, but the later ones don't. In contrast to that, my comcast address, although beginning with "r", which is after the smaller domains stop delivering, goes through fine.
- Hotmail, as far as I can tell, does not go through even to my Hotmail address that begins with a "d". As stated above, hotmail shows as dsn=2.0.0, stat=Sent ( <21431207.1095024967457.JavaMail.root@mail.ceocast.com> Queued mail for delivery), where AOL just says sent with no queuing.
- On the nightly run, I see my Hotmail address as queued, but I receive the email almost immediately, every time.
I believe it's a queue saturation problem, or maybe even messages getting dropped from the queue. I'm very familiar with both the sendmail.mc and the sendmail.cf files, having crawled through them more than a few times, so I can tell you what various settings are, if you need to know.
Thank You. This one's very important, as it's a final problem in the list of more than a few.
Next, lotsa HTML is one of the things that SPAM filters look for. If what you have to say is really worth reading, you don't need HTML. A link or two is fine, but much more than that and SPAM filters tend to perk up. Same for multi-part messages that are just repeats (MIMEdefang/SpamAssassin has specific filters for that garbage).
Make sure your mailhost is properly registered in DNS, with a reverse-lookup record, and is listed as a Mail eXchanger.
Since you seem to be able to send out smaller amounts of E-mail fine, consider breaking the 80K honker into smaller jobs spread over several hours. You can pretty much guarantee that Hotmail throttles connections after X number of RCPT TO: requests during the SMTP conversation. And you can also guarantee that Hotmail's servers are configured to keep tabs on who sends them how much E-Mail, and regard lotsa E-Mail from one place in a short time as a spammer.
If Hotmail offers its users a white-list feature (I have no idea, never used Hotmail), encourage your subscribers to white-list you.
And quit sending text part/html part duplicate E-Mails.