smtplib sendmail problems

Peter Hansen peter at
Mon Feb 9 21:07:51 CET 2004

Hank wrote:
> I have a function that sends mail but I'm finding the number of
> characters in the To: field is limited to ~255 characters. This means
> that email is sent to only part of the email list.
> #recipients is a list of email addresses, greater than 255 characters
> in total
> header = "To: " + string.join(recipients, "; ") + "\r\n" \
>          "From: " + "testing at\r\n" \
>          "Date: " +  time.strftime("%A, %B %d, %Y %I:%M %p",
> sendTime)+ "\r\n"
>          "X-Mailer: Automated Test \r\n" \
>          "Subject: " + subject + "\r\n\r\n"
> text = header + mailText
> server = smtplib.SMTP('')
> result = server.sendmail("testing at", recipients, text)
> server.quit()

What does "recipients" contain?  That's the relevant thing here,
not the To: header.

SMTP does not use the To: header for any purpose.  In fact, it can
be absent.  If only some people are receiving your message, it is
something to do with the recipients list (note: it must be a list)
and not the header.  Or there's a problem with an intermediate 
mail relay.  Or something else.  Always lots of ways for this stuff
to fail except, generally, the To: header.


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