Odd addition to email Subject line ***UNCHECKED***

[David27c 0]

Hi everyone. This is my first post here; hope it's in the right place!

On my SONY  Xperia XZ Premium (Android 9), I got a strange phrase added to the beginning of the Subject line on a msg I sent.

***UNCHECKED***

Haven't a clue where this came from, or who's to blame - me, the Sony email client, my ESET Mobile Security app, or - as usual - the Government.

The first I knew of it was when the Recipient asked me what it was.

It hasn't recurred.

Has any one else experienced this phenomenon?

Many thanks.

Saturday 6 Jun 2020 2046hrs BST.

[Marcos 5,074]

Since applications (including AV) cannot access the content of other applications, the string must have been added on the mail server.