[AC Question]

Gmail combines all e mails with the same subject. Therefore Gmail is not suitable for professional use (MAILING LISTS), unless this mode can be switched off.

Combining e-mails is thinking in the sense of private use and not professional use.

Anyone who can help me to advise how to switch off this conversation mode ?

[Rukbat]

Email threads by topic - that's the default for email. (Email isn't texting.) If you want it to thread by date or sender, you'll need an email app that's been written to do that - which is very rare, since that's not how email is designed to be used.

It's not personal/professional, it's the thread is about the subject. If you're discussing 3 subjects with one person, you don't want a thread of different subjects. That's not how we talk to people, changing topics every sentence. We talk to one person, or to a group, about one topic, until we're done talking about that topic.

Texting takes the other approach - everything between you and one person is grouped as one "conversation" (even though it's not many times).