Several test mails later, I didn’t receive any e-mails at all. Tried different settings, but nothing seemed to help. After reading some forums, I read a suggestion about looking in the All Mail folder. There I saw the emails. However, these were the mails I sent, not the ones I should have received. I was puzzled.
After reading some more I finally found out what was going wrong: I was sending emails from my Google address to another Google address which is actually an alias of my address. Google thinks that I’m receiving mails from myself, which are blocked. Why? Google tries to block these kind of messages thinking they are meant for mailing lists etc. Workaround? I’ve found out that if you add the alias email account to your accounts, the Google rule is circumvented and the mail does arrive.