Lost service desk mails

With gitlab.com, and an e-mail address that aliases to the service desk address, there are randomly certain e-mails that never reach the service desk. I’ve set up an additional e-mail address that also receives the e-mail since they sometimes don’t actually arrive in gitlab. Some of them do, some of them don’t (so the alias itself seems to be working just fine). As this is with gitlab.com, on an open-source repository (so free account) I’ve been unable to reach support.

Anyone else having this issue? Thoughts on ways to solve it?