Python: when sending email, always blocked in the clause: smtpserver = smtplib.SMTP(“smtp.gmail.com”,587)

Question

I am writing a Python program to send an email. But every time when executing the clause:

smtpserver = smtplib.SMTP("smtp.gmail.com",587)

it will block here and always stay the executing status without any prompts and errors. I don't know why. And can anyone help me?

The code is as following: import smtplib

to = 'toemail@gmail.com'
gmail_user = 'user@gmail.com'
gmail_pwd = 'password'
smtpserver = smtplib.SMTP("smtp.gmail.com",587)
smtpserver.ehlo()
smtpserver.starttls()
smtpserver.ehlo
smtpserver.login(gmail_user, gmail_pwd)
header = 'To:' + to + '\n' + 'From: ' + gmail_user + '\n' + 'Subject:testing \n'
print header
msg = header + '\n this is test msg from mkyong.com \n\n'
smtpserver.sendmail(gmail_user, to, msg)
print 'done!'
smtpserver.close()

Answer 1

Maybe I am 4 years late, but this is what worked for me and might help someone else!

server = smtplib.SMTP("smtp.gmail.com", 587, None, 30)

Answer 2

There may be some issue with the connection (maybe it is being blocked by your proxy or firewall?) and the timeout may be pretty big for you to do not see it going further.

The documentation of smtplib.SMTP says:

class smtplib.SMTP([host[, port[, local_hostname[, timeout]]]])

(...) An SMTPConnectError is raised if the specified host doesn’t respond correctly. The optional timeout parameter specifies a timeout in seconds for blocking operations like the connection attempt (if not specified, the global default timeout setting will be used).

Try specifying the timeout yourself:

smtpserver = smtplib.SMTP("smtp.gmail.com", 587, timeout=30)

Answer 3

For reference, cpython smtplib is blocking. That is, it blocks the GIL (ie Python) while connecting. Despite the claims the GIL is released on I/O, it is only released on some I/O, and SMTP connections are not such. To make it async, you need to hand the mail send to another process or thread, depending on your situation.