Without extension

[ozzii]

I tried, but without success, to create a filter who hide all the subjects without extension.

It's for not showing (for example) the request message.

Any advice, please

[bobkoure]

By extension you mean like in DOS and windows dot-char-char-char? With either a newline, tab, or space trailing the extension?
How about
\.\w{3}\W

If you want to match the above plus dot-char-char-char-char (as in .flac and .divx)
\.\w{3}\w*\W

I've just tried this in the find window and it seems to work fine.

[Quade]

It supports the {2-4} syntax too.

[ozzii]

Yes, I mean like in dos.
I will try that thanks.

[bobkoure]

Based on Quade's comment you can also use
\.\w{3-4}\W
where 3-4 means at least three but not more than four characters following a dot -

[edit]
actually, that will miss extensions at the very end of the line (that trailing \W means an actual non-word character) - instead, use
\.\w{3-4}\b
where \b just means a word boundary, which could be the end of the line
[/edit]