English CAE formal or informal?

What about trying

Informal

Why not try

Informal

Additionally

formal

Also

formal

Furthermore

formal

I am writing with reference to your letter

formal

I hope to hear from you at your earliest convenience

formal

I look forward to hearing from you without delay

formal

I suggest that

formal

I urge you to

formal

I would like to offer congratulations on

formal

In my opinion

formal

It is recommended that you

formal

Let me congratulate you on

formal

Moreover

formal

Personally, I have no doubt that..

formal

I hold the view that

formal / informal

As well as that

informal

Better still

informal

Do drop me a line if you have time

informal

Hope to hear from you soon

informal

If I were you

informal

It was freat to hear from you

informal

Keep in touch

informal

My own thoughts are

informal

Thanks fow writing to me

informal

Then again

informal

To my mind

informal

What's more

informal

You could

informal

well done!

informal