5.7.1 Not authorised to send from this header address

Hi,
I’m migrating from Thunderbird to Em Client, and the only thing I cannot get to work is sending emails from aliases. My main email address is my work email, but I also use my personal gmail account as an alias.

I can send from the alias gmail account to my work email, but if I use the gmail alias to send to another gmail account (or any other domain for that matter) I get the error “5.7.1 Not authorised to send from this header address”.

I am using IMAP with Fastmail as my mail server.

Any idea what is causing this?

Log:

11:08:23 br@companymail.com SMTP Connecting: To br@companymail.com
11:08:24 br@companymail.com SMTP Connected: To br@companymail.com
11:08:24 br@companymail.com SMTP Sending messages
11:08:24 br@companymail.com [SMTP] MailClient.Storage.Application.ItemOperationException: Cannot send message (Email body not accepted due to the following reason: 
             "5.7.1 Not authorised to send from this header address
         ")
           GUIStatus_Exception_Reported = True
11:08:25 br@companymail.com [SMTP] MailClient.Storage.Application.ItemOperationException: Cannot send message (Email body not accepted due to the following reason: 
             "5.7.1 Not authorised to send from this header address
         ")
           GUIStatus_Exception_Reported = True
11:08:25 br@companymail.com SMTP Disconnected: From br@companymail.com
11:08:25 br@companymail.com SMTP Disconnected: Done
11:08:28 br@companymail.com SMTP Connecting: To br@companymail.com
11:08:29 br@companymail.com SMTP Connected: To br@companymail.com
11:08:29 br@companymail.com SMTP Sending messages
11:08:29 br@companymail.com [SMTP] MailClient.Storage.Application.ItemOperationException: Cannot send message (Email body not accepted due to the following reason: 
             "5.7.1 Not authorised to send from this header address
         ")
           GUIStatus_Exception_Reported = True
11:08:30 br@companymail.com [SMTP] MailClient.Storage.Application.ItemOperationException: Cannot send message (Email body not accepted due to the following reason: 
             "5.7.1 Not authorised to send from this header address
         ")
           GUIStatus_Exception_Reported = True
11:08:31 br@companymail.com [SMTP] MailClient.Storage.Application.ItemOperationException: Cannot send message (Email body not accepted due to the following reason: 
             "5.7.1 Not authorised to send from this header address
         ")
           GUIStatus_Exception_Reported = True
11:08:31 br@companymail.com SMTP Disconnected: From br@companymail.com
11:08:31 br@companymail.com SMTP Disconnected: Done

Your server doesn’t allow you to send from that address when you are logging into their server using your work address.

So if you login using br@ you can only send from br@

It worked with Thunderbird and I imported those settings into Em Client.

Aliases are different in Thunderbird. They each have their own SMTP account so not the same thing.

Okay. So what am I missing here. What good are aliases in Em Client if you cannot send emails using them?

An alias is an address that your email provider allows you to send from using a different account SMTP server. It is dependent on your email provider, and not the email application you use.

You normally can’t just send from any old address and expect your email provider to allow that. Some may allow you to send from a different email address but they will include in the message header that the message was sent from br@.

You will need to contact your email provider and find out if they will allow you to send from other addresses through your br@ account.

Got it. Thanks Gary.

It seems I must have had gmail configured as an extra SMTP server in Thunderbird. Creating my gmail address as an alias through Fastmail’s web interface allows me to send using my gmail address from Em Client.

Thanks again.