My emails arrive twice, but why?

TidBITS Talk
1

An email contact of mine in a 100-people company with good IT receives my emails twice, with a time difference. The emails show in Apple MAIL on my Mac in the SENT folder once, on the mailserver in the SENT folder twice.
One double arrived 3 mins later, another double arrived 15 mins later. No other person gets my emails twice.
There is no alcohol involved. :grinning:
I did however use the delayed sending feature for both of these.
Ventura 13.6.7

How come?

1 Like
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We need more informationā€¦

  • Which ISP are you using for mail?
  • Do you use IMAP, or POP?
  • Since you said ā€œon the mail server in the SENT folderā€ I assume your ISP has some form of webmail. What happens if you use the webmail to send the message?
  • Does the problem occur if you donā€™t use the delayed sending feature?
  • Do you have any Mail plug-ins?
  • Do you have more than one Apple device? If so, does the problem occur on them also?
  • Do you have any other SMTP servers you can try (e.g. another ISP or iCloud)?

The way I think it is supposed to work is while the message send is waiting, it is held only in Mail, which is why it doesnā€™t appear on Mail on any other device.

One difference, though, is it isnā€™t Mail thatā€™s sending the message! It is maild, a daemon. That makes sense, since you might not have Mail open at the time the message should be sent.

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  • Which ISP are you using for mail?

A UK hosting provider using an Exim mailserver, like many, many others.

  • Do you use IMAP, or POP?

IMAP

  • Since you said ā€œon the mail server in the SENT folderā€ I assume your ISP has some form of webmail.

Yes, Roundcube

  • What happens if you use the webmail to send the message?

Not tried.

  • Does the problem occur if you donā€™t use the delayed sending feature?

Interestingly, no doubled email get sent.

  • Do you have any Mail plug-ins?

none

  • Do you have more than one Apple device? If so, does the problem occur on them also?

I have, but havenā€™t tried.

  • Do you have any other SMTP servers you can try (e.g. another ISP or iCloud)?

I also have Gmail, but hardly ever use it for business and donā€™t really want to try with this client because they would ā€œlearnā€ about the Gmail address which I donā€™t want them to use. But I did check all respective SMTP settings which are all OK.

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Another thing that would be interesting is to see is the raw messages in the ISPā€™s sent folder. And compare to the raw message in Mailā€™s Sent folder.

I wonderā€¦

Letā€™s say we are using IMAP, and send a message from Mail. How does it get to the Sent folder? There are two possibilities:

  • Mail sends the message through SMTP. The ISP copies it to Sent. Then it shows up in Mailā€™s Sent when IMAP syncs.
  • Mail sends the message through SMTP. Mail copies the message to Sent, which then syncs to the ISPā€™s Sent through IMAP.

So what happens when the maild daemon sends the message? I know that it access both the SMTP and IMAP servers.

Iā€™m wondering if it is possible that the ISP is seing the message go out through its SMTP, and so it it to the Sent folder, but then the maild also adds it. Is there some kind of duplicate detection that normally deals with this?

Hereā€™s where we need more knowledgable people to weigh inā€¦

5

I looked in to the raw source (and can provide it, if somebody wants to have a look)
I think that the main suspect here might be the delayed SEND function of Ventura.

My first msg was an answer to a previous email, this makes headers longer and more complex. However, both, the msg and its duplicate carry the same X-Universally-Unique-Identifier.

My 2nd msg was a new email from scratch = simpler headers. Again, both the original msg2 and its evil twin share the same X-Universally-Unique-Identifier:

This fact speaks now against my theory about the delayed SEND function of Ventura and I am nonethewiser.