Mailing List Message #106158
From: Bill Cole <>
Subject: Re: SMTPUTF8 in MAIL FROM command
Date: Tue, 30 Aug 2016 22:39:07 -0400
To: CommuniGate Pro Discussions <>
X-Mailer: MailMate (1.9.5r5251)
On 30 Aug 2016, at 12:34, Jeff Wark wrote:

I have one customer that is attempting to send email using Outlook 2016 (I think).  Their MAIL FROM command looks like this:

10:09:47.618 4 SMTPI-548278([]) cmd: MAIL FROM: &lt;; SMTPUTF8
10:09:49.621 4 SMTPI-548278([]) rsp: 555 syntax error in MAIL FROM parameters
10:09:52.136 4 SMTPI-548278([]) cmd: QUIT

Is that some standard that we (CommuniGate server users) should be accepting at this point (the SMTPUTF8 string at the end of the command)?

No. No version of CGP supports SMTPUTF8. SMTPUTF8 is not indispensable for anything, or it would have happened a decade faster. No mail server that does not support SMTPUTF8 should accept it as an extra argument to MAIL. This is true of all SMTP extensions that use MAIL arguments: it would cause worse issues further along if receivers just accepted extensions they don't really do.

I am using CommuniGate 6.0.11 right now, but I can see no mention of the string SMTPUTF8 in the history for versions 6.0 or 6.1.

According to, one feature of this extension is that email addresses containing non-ascii characters can be used.  However, not many mail servers seem to support it.

Yes. There is also a clear simple mechanism by which clients can tell whether SMTPUTF8 is supported before just trying it, which is the same mechanism ALL SMTP extensions use. It would take a totally incompetent MUA developer to send SMTPUTF8 in MAIL after not seeing it in the EHLO reply.

So, yeah: Only Microsoft. No surprise there.

Again, looking in my logs, I can see only one customer attempting to use it at this point.

Anyone else have experience with this?

Not with CGP, but I run Postfix instances that have it enabled. It is pretty rarely used. I don't believe I've ever accepted a message using it, but those are high-spam low-total volume systems.

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