As an Asp.Net server control, the Membership Manager
Control includes a width
property that defines its normal width on your administrative web page. If
you set the control to a narrow width and have members with very long Email addresses,
you may encounter an issue where the width of the control expands beyond its specified
size.
Long passwords without a word break do not wrap in HTML
As illustrated below, a long Email address without any word break characters (spaces)
does not word wrap in HTML. This causes the control to expand beyond its intended
control width.

Notice the slight ridge of
the control’s outside border. The control renders as HTML and therefore has the
limitations of HTML tables, divs and other formatting elements. In the case of users
with very long Email addresses, there is really nowhere to break the line.
We decided
against introducing random spaces or characters that would allow line breaking to
occur.
Recommendation
Set the control width to the maximum size possible or place it onto a page that
allows for "growth".
Related Topics
The Membership Manager Control
Membership Manager Configuration