You have a setting in the gmail webmail account that is doing this.

Check to see if you have any filters set up with "Never send to spam" that might be matching your sent messages.

This can send sent messages to the Inbox. In gmail webmail account: To access filters: Gear icon -> "Settings" -> "Filters and Blocked Addresses" tab.

Do you use send using alias email addresses...read this: https://support.google.com/a/answer/1710338?hl=en

Hi Toad-Hall,

I have no filters setup, and no blocked email addresses either. I am not using the "send mail as from another account" facility.

The sequence is this: 1) I send an email to someone using web gmail. 2) A copy of the sent email appears in my Thunderbird Inbox when Thunderbird next does a "get messages" from gmail, using POP.

I'm now wondering if it is in fact normal behaviour?

Pop accounts can only access and download from the gmail Inbox, so gmail must be putting the email in the server Inbox. It is not normal to have sent emails put into the Inbox.

In Gmail filters an action of "never classify as spam" apparently also applies to sent messages and automatically assumes unless you specify another it will put it in the inbox.

Try:create a new filter, with your address in the "from" field, and marked "skip inbox".

Also check: I located someone who said: I have problem of a copy of my Gmail sent mail showing up in my Inbox. Go to Gmail - Settings - Forwarding POP/IMAP - POP Download. Find the question "when messages are accessed from POP (options). Mine had (keep Gmails copy in Inbox). It is a drop down box so you have options.

No, Gmail is not putting the sent email into Gmail's inbox. It is put where it should be, in Gmail's sent folder. I've just double-checked this.

I've tried your suggestion of creating a new filter on messages where my own email address is the sender, applying the "skip inbox" action (and no other actions). It makes no difference. I think this proves that it is nothing to do with gmail's inbox. Somehow POP is getting the message from the sent folder.

Your final suggestion of looking at the "when messages are accessed from POP (options)" is of little use. I want all messages to remain in gmail's inbox as well as being popped to my own PC, so it is set to "keep Gmail's copy in Inbox".

It is impossible for any Pop account to get anything from the server 'Sent' folder. No Pop mail accounts on any server get access to anything except the Inbox regardless of whatever email client you use.

It is well known for gmail to put emails that you send into both the Sent and Inbox server folders. But there are a few different ways it can occur and it is a question of working out which one is causing it in your case. This is not a Thunderbird issue and really you should be asking this on the gmail forums.

I only know about these that can cause it. In webmail: Are you using Settings->Accounts->Send mail as to send "from" another address? Clicking the option to "treat as alias" will force the message to the Inbox. So if you have two gmail email addresses and you can send using either of those email addresses in that same webmail account, then it is possible one is set up to be able to send as an alias. Do you have some Email addresses in the Accounts section? If yes, then you know the cause of emails in the Inbox.

In Gmail filters an action of "never classify as spam" apparently also applies to sent messages and automatically assumes unless you specify another it will put it in the inbox. Try:create a new filter, with your address in the "from" field, and marked "skip inbox".

re : If I use my smartphone to send an email (using aquamail), it's fine, the email ends up in the sent folder on gmail without a spurious duplicate appearing in my Thunderbird inbox. If you use a gmail email address to send emails, then gmail will automatically put a copy in the server Sent folder. Does the smart phone access gmail via POP or IMAP?

Good info on POP and gmails weird methods of allowing access to pop using more than one computer/email client to access mail. If pop, are you using the 'recent' or 'normal 'mode ? https://support.google.com/a/answer/6089246?hl=en

In Thunderbird: If you want to pop messages and leave a copy on the server, you need to set that instruction in Thunderbird Account Settings > Server Settings for that gmail account.

• Right click on pop gmail account name in Folder Pane and select 'Settings'
• select 'Server Settings'
• select checkbox 'Leave messages on server'
• click on OK
• Restart Thunderbird to ensure settings are being used in current session.

You are right. This should be on the gmail forum. But if, as you say, gmail has put the sent message in its inbox, why, when I look on gmail, do I find it's actually in the Sent folder?

I believe I've found the answer here... https://support.google.com/mail/forum/AAAAK7un8RULD7xm9IbGT4/?hl=en-GB

Gmail DOES copy sent emails to the POP download queue if the email was sent from the gmail web app, but not if it was sent from another client using SMTP, such as my mobile phone.

All very inconvenient if you want to store all your emails, received and sent, on your PC.

Sancho Panza said

All very inconvenient if you want to store all your emails, received and sent, on your PC.

not really I am sure you can craft a Thunderbird filter that can identify mail from you in the inbox and move it to the sent folder. That is why they do such things, so you have a local copy.

Matt said

not really I am sure you can craft a Thunderbird filter that can identify mail from you in the inbox and move it to the sent folder. That is why they do such things, so you have a local copy.

Okay I've worked out how to do that and it's successful for emails that were originally sent on the gmail web app, but emails originally sent on my phone don't show up . They get as far as the sent folder on gmail (as seen from the web app) but they don't get forwarded to Thunderbird.