there is nothing to "wait for". she is not coming back, my friend
to do what you want the way you're sending an email, you need StartActivityForResult and
an email client that returns a result. StartActivity does not do that, and it's unclear if your
email client knows how to return a result to somebody that is waiting. i hope your understand
this.
if you have access to an smtp server, you can use the Net library to send email from within
your app. that library tells you if your email was successfully sent. then you can continue.
by the way, successfully sent does not mean received by the recipient. it just means the
recipient's mail server reports no errors. the recipient's server and/or the recipient could have
spam filters in place. there would be no error if the mail were quietly deleted.
try the Net library
https://www.b4x.com/android/forum/threads/new-net-library-android-ftp-smtp-and-pop3.10892/#content