In the section "How to avoid submitting the same message to both the outgoing mail server and the incoming mail server?" a common approach of sending a BCC copy to self is not mentioned.
For example, Thunderbird in Account settings offers an option to "Bcc these email addresses: ". When checked, the default value is your own address.
Delta Chat offers an option to send BCC copy to self as the only option to store copies.
In the section "How to avoid submitting the same message to both the outgoing mail server and the incoming mail server?" a common approach of sending a BCC copy to self is not mentioned.
For example, Thunderbird in Account settings offers an option to "Bcc these email addresses: ". When checked, the default value is your own address.
Delta Chat offers an option to send BCC copy to self as the only option to store copies.