smtplib send mail dns resolve problem

[星星]

On 10月19日, 下午11时05分, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> En Mon, 19 Oct 2009 05:44:14 -0200, 星星 <starstarstar... at gmail.com>  
> escribió:
>
> >     my email smtp server hostname can be parsed to 5 ips, for example:
> >     ******************************************************************
> >      my email smtp server hostname:  email-my.local.com
> >      ips through dns parse:
> >     1.1.1.1
> >     1.1.1.12
> >     1.1.13.1
> >     1.1.1.14
> >     1.1.1.15
> >     ******************************************************************
>
> >     but when i send mail using smtplib, i was always using one ip, no
> > dns re-resolve happened, (for example: only use 1.1.1.12). I checked
> > smtplib src code, but i can't find anything strange;
>
> smtplib does not issue a dns query for a MX record, if that is what you  
> were expecting. In fact, the Python standard library does not contain any  
> module for DNS handling.
>
> >     for i in range(1000):
> >         server = smtplib.SMTP(host)
>
> Here, `host` is used directly -- whatever address gethostbyname returns.  
> If you want load balancing among the 5 addresses above, you'll have to do  
> it yourself:
>      host = random.choice(list_of_addresses)
>
> If you don't want to hardcode the addresses, there are a few libraries  
> that perform DNS queries in PyPI.
>
> --
> Gabriel Genellina

thanks very much! I tried your suggestion and it worked!

But I still wonder why gethostbyname returns the same address all the
time(maybe 50000 times).