Not receiving mail sent through PHP SM_SMTP, but can get mail when sent through same server via telnet

Question

Having heard so many bad things about PHP mail() I skipped it and downloaded kid moses' SM_SMTP class. This seemed easy enough to config. server, port, user, password etc. But when I tested it I received no mail.

So I turned on the debug flag and tried again. I get the following:

334 UGFzc3dvcmQ6
235 2.7.0 Authentication successful
250 2.1.0 Ok
250 2.1.5 Ok
354 End data with .
250 2.0.0 Ok: queued as 4C33993A54
221 2.0.0 Bye 

queued so everything looks fine. But still no email. So I telneted to the server:

AUTH LOGIN
334 VXNlcm5hbWU6
enc 64 username*
334 UGFzc3dvcmQ6
*enc 64 pwd*
235 2.7.0 Authentication successful
MAIL FROM:[email protected]
250 2.1.0 Ok
RCPT TO:*email address*
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
TEST
 250 2.0.0 Ok: queued as 3B75693A54

looks much the same. again queued. but this time I received it ASAP.

So:

1. Does anyone use kid moses SMTP class? Is it good? the docs seem competent
2. Should I try mail? Can anyone recommend best practice for PHP mail?
3. How would you go about investigating further?

NB I mailed the log to my host provider but they just respond with some 'please provide a complete description of how to replicate BS'

Answer 1

Ok, I have come to the conclusion there is at least one silent spam filter opearting here. The test email went because he content was just TEST and the filter was fine with that. The candidate production emails contain HTML. Changing the destination from a hotmail account to a gmail account without any changes to config or script causes email to arrive (albeit still with spam notice).