```
  File "mail.py", line 9, in <module>
    smtp_server.starttls(context)
  File "/usr/lib/python3.6/smtplib.py", line 748, in starttls
    self.ehlo_or_helo_if_needed()
  File "/usr/lib/python3.6/smtplib.py", line 600, in ehlo_or_helo_if_needed
    (code, resp) = self.helo()
  File "/usr/lib/python3.6/smtplib.py", line 429, in helo
    (code, msg) = self.getreply()
  File "/usr/lib/python3.6/smtplib.py", line 393, in getreply
    raise SMTPServerDisconnected("Connection unexpectedly closed")
```

This happens due to the server expecting commands (like EHLO, STARTTLS) being strict upper-case. And when the SMTP command isn't, it drops us.

This is a rare edge case since most mail servers handles shady client data in numerous different ways (such as gmail never sending QUIT for instance).

I don't know of a work-around for this and the documentation states `EHLO` is being sent (https://docs.python.org/3/library/smtplib.html), so I guess the lib assumes that's the case as well.

Turns out, this goes for a lot more commands, such as:

```
Traceback (most recent call last):
  File "mail.py", line 12, in <module>
    smtp_server.sendmail(fromaddr, toaddrs, msg)
  File "/usr/lib/python3.6/smtplib.py", line 866, in sendmail
    raise SMTPSenderRefused(code, resp, from_addr)
```

The command that the server refused was:

    mail FROM:<my_mail@gmail.com> size=11

Again, this is mostly because traditionally server commands are upper case (even tho RFC 821 defines that they can be any syntax, such as `mAiL FroM`).

But it would be nice if Python could keep consistency in it's syntax IMHO.

It is interesting that in all the years smtplib has been in use, this is the first time (as far as I know) this has been reported as a problem.  I don't see any reason to object to changing it to send the commands in upper case, but the server you are talking to is definitely out of spec with the RFC :)

Seeing as I'm the one who built the server, it sure is out of spec :)

I could also quickly correct for this "issue" server-side.
So this is more of a "style guideline" change client-side - If no one opposes of keeping commands stylistically the same.

On the other hand, the current mixed case sending found a bug in your code, so it has some value.  I'm neither in favor nor in objection to the change, at this point.

Is EHLO the only command sent in lower case?  I think it might not be.

I suppose I'm a solid ±0 on changing this (how's that for a completely neutral endorsement?).  I won't do the change myself, but I'd review a pull request.

It's been 5 years, it's not really a bug, and nobody seems to be interested enough to submit a patch so I'm closing this. Feel free to reopen if you want to pursue this.