Hi, christian,
here some explanations.
I have a survey, the link of which I will send around to various people.
You are going to send the generic link (like:
www.myServer.de/survey/index.php/228362?lang=de
to some participants - an open survey without tokens.
So there is no email anywhere.
The assigning of numbers and passwords is great, and it works.
Here you talk about the case that the participant wants to stop and resume later, don't you.
He is asked to enter some credentials like a username and a password. These are values he likes, he thinks will be useful, or whatever.
Only if the participant is afraid to suffer from Alzheimer disease he may enter an email address where these credentials are sent to.
These credentials are not saved in the answer table, but in a different table of the database ("lime_saved_contol").
If the participant continues later and completes the survey these data are removed from this special table.
Like this
'if you put your email here, we will send you the tokennumber and the passwordnumber, and you can later on access your data, but we will not save the email'
The email is only saved as long the participant did not complete the survey.
So this is not a problem at all. This is the standard behaviour.
The other thing is that - as I understood - you want to sent some other things to the participant. Here the participant has to enter his email address which has to be stored in the answer table. Unfotunately LimeSurvey has no feature to send an email "in the middle " of the questionnaire, as some other tools have (e.g. in CATI interviews the interviewer sends a mail to the respondent during the interview to be able to visualize something).
This way you would have the chance to send the message and later - with a question of type "equation" you empty the field where the email address was stored. There was a question like this some time ago in the forum.
In LimeSurvey you can only use one of the both types of confirmation email or you use the plugin pdf-report to send a customized report of the participant's answers. But these are sent after completion.
If you are a bit experienced with php you could use an ajax call to send during the survey.
But as long we do not konw more about this - what you are going to send - I cannot say more.
Joffm