[SPAM] Re: Threaded alternatives to smtplib?

MRAB google at mrabarnett.plus.com
Mon May 4 09:57:51 EDT 2009

Diez B. Roggisch wrote:
> Alex Jurkiewicz schrieb:
>> Hi all,
>> I'm writing a Python script to do a "mail merge" style email 
>> distribution. I create a few python threads and in each one I call 
>> `smtpserver = smtplib.SMTP(our.smtpserver.com)`. However, during the 
>> sending process, there seems to be only one connection open to our 
>> mail server at any one time. In other words, all these threads gain me 
>> no speed benefit at all!
>> I seem to be running into the issue where smtplib is not fully 
>> thread-safe, as mentioned in this thread:
>> http://mail.python.org/pipermail/python-list/2007-March/429067.html
>> http://mail.python.org/pipermail/python-list/2007-March/429172.html
>> Does anyone have suggestions as to a suitable workaround for this 
>> issue? I was looking at the Twisted library, which seems possible but 
>> significantly more complex.
> I doubt that there is such issue. The above discussion is not concluding 
> that there actually *are* threading-issues within smtplib. And looking 
> at the source of smtplib, it certainly doesn't use any 
> locking-primitives or (directly) any c-extension that might explain such 
> behavior.
> Without more code, it's impossible to tell if there is anything peculiar 
> in your usage of the lib. Maybe you close your connections to fast to 
> see several open?
If all the threads are using the same server, couldn't the SMTP part be
put into its own thread and then fed the pre-composed emails via a

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