Sending email to AOL's smtp server fails with "501
INVALID SASL FORMAT OR LENGTH".

This patch allows the default order (AUTH_CRAM_MD5,
AUTH_PLAIN, AUTH_LOGIN) used to select the AUTH method
to be overridden with a new optional preferred_auths
parameter.  By changing the order so that AUTH_LOGIN
comes before AUTH_PLAIN, AOL's smtp server is happy. 
This patch may be useful for other stmp servers that
fail on login when using the default AUTH selection order.

Sample usage:

if aol:
    auths = [smtplib.AUTH_CRAM_MD5, smtplib.AUTH_LOGIN,
smtplib.AUTH_PLAIN]
    smtp.login(fromUser.split("@")[0], passwd, auths)
else:
    smtp.login(fromUser, passwd)

I tested the patch using python 2.4.3 on slackware 10.2
 (kernel 2.4.32).

This seems reasonable to me; the preference of which authentication modes to use shouldn't be a hardcoded decision in smtplib, especially if one of the biggest email servers around breaks if we can't.

However, I think it needs a couple things done before it should be accepted:
  #1) The code patch itself needs to be done against the trunk, as it doesn't currently apply cleanly (it's a trivial fix)
  #2) The documentation patch should include mention of the "constants" of smtplib.AUTH_*

File Added: smtplib.patch