Expiration mark 'E' disappearing

[romeomedina]

Hi.

In the summary buffer:
I mark a message as expirable with 'E', then get back
to the group buffer with 'q', and then when I get back into
the summary buffer the mark 'E' has disappeared.
Is that normal? If the mark is not there any more,
how do I know that an article is marked as expirable?

Excuse such a basic question, I couldn't find a solution
in gnus manual.
Thanks for any reply,
Rodolfo