Not so Hot Mail
Just last week I was chatting with a friend, and I sent a photo to him using his hotmail address (yes, MSN/Adium filetransfer is horrible). After a couple of minutes he got back to me saying that he still had not received anything. This seemed strange: usually everything that I send using my own mail server arrives instantly. I use it everyday and never had problems with delivery. I blamed it on Hotmail servers being probably very busy filtering and/or delivering all the junk email that they regularly get.
Then a couple of days later the same thing happened with someone else: mail did not get delivered to his Hotmail address. He also had a GMail address, which delivered instantly. So I started investigating what could possibly go wrong, since I did not get any failure emails back. The postfix’ log proved my suspicion, nothing went wrong on this side:
postfix/smtp[36741]: C9D372E03B: to=<***@hotmail.com>, relay=mx3.hotmail.com[65.54.245.72]:25, delay=25, delays=3/0.03/0.57/21, dsn=2.0.0, status=sent (250 <466406F3.6030701@ je-ju.net> Queued mail for delivery)
Then I checked sending to a test account of my own. The message got sent correctly, but nothing apppeared in the inbox, nor in the junkbox. Even adding the domain to the trusted senders did not help one bit.
So I turned to the Hotmail FAQ pages. They have some nice pages specificaly aimed at postmasters. The tips there include checking your own mail server, and implementing SPF/SenderID (with lots of disclaimers that SPF/SenderID itself will not guarantee delivery). There is also a form where you can contact their support.
A word of warning about their support: if you have read the FAQ (like you should) you can just as well ignore their first reply and restate your question again. The first reply you get will be a pure copy & paste of most of the FAQ. The second reply suggested that I implement SPF (with the disclaimer that SPF/SenderID will not guarantee delivery), while I had carefully explained that my DNS provider does not allow that. A more helpful suggestion was to send represenative messages to randomtestacct@hotmail.com, which would help training their spamfilters.
Note that my mailserver is for private use only. My girlfriend and I are the only people who use it, and we rarely send messages to Hotmail accounts, and when we do, this will purely be personal communication. We have never used the mailserver to do any kind of commercial messaging. So there was no reason for me to suspect blocking, nor has there been any kind of warning from Hotmail.
When I checked back a day later, my test messages had mysteriously appeared in my Hotmail inbox, even those sent before I sent a message to that test account.
So everyone with a Hotmail address is hereby warned: emails to you can and will be filtered at will by Hotmail, without anyone knowing about this. You should be very careful about drawing conclusions when you are not receiving emails you are expecting…