I have sent out 5 different edm with different content to a group of people. 4 of them could reach the mailbox of yahoo, gmail and hotmail successfully.
The problem is that the remaining 1 being flagged as SPAM by hotmail. (It can reach the mailbox of yahoo and gmail successfully)
Does anyone know why?
This can be down to a number things.
If you sent the emails out quite quickly then the receiving email server may just flag it as spam.
The other thing that it could be is that you are using a phrase that the hotmail spam filter is picking up on. I suggest running your email through something like spamassassin to see what it would score.
If its still got a good score then maybe you need to be affiliated with the hotmail feedback loop so that they can let you know when someone hits "This is spam" button.
IF that doesnt work then you may need to see if your IP address has been blocked by hotmail. If you want to do email direct marketing, the IP address normally has to be whitelisted by the email provider and potentially spamhaus so they know you aren't a spammer.