When it comes to problems with emails, experience here in the forum has shown, that the problem was mostly with the email server or the email settings. Otherwise we would have a lot of complaints here in the forum, if there was something wrong with the email functions of Limesurvey. So you will need to try with different email accounts (always go for SMTP) and see if one works, then check what is different with this email account than with the others. As we have no access to your server installation, there is very little we can do here in the forum, besides the hints we already gave.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
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