This can be due to different reasons:

• Email was not sent successfully from sender’s side. Please contact sender’s service provider to confirm.
• Email might have been lost due to networking issue or a technical error at one of the (email) relays. Nothing much can be done here. Best would be to ask sender to try again. In case the problem persists, then contact our support.
• Email might have been regarded as spam, and moved to Spam folder. Please check your Spam folder (emails in this folder are subject to auto-deletion).
• Email might have been filtered and not available in Inbox folder. Please check your incoming email filters to confirm.
• Email might have got a high spam score and hence was refused at reception time. This is to better protect our users from abuse and fraud. Please ask the sender to follow good practices.

Alternatively, you whitelist sender address or domain in a paying plan.

In case none of the above points help, or if you think an email was wrongly refused (e.g., a false-positive), then please send an email to our support with:

• Full headers + body or archive of the email that never arrived (you will need to contact your sender to share that with you)
• If above is not possible, then at least the date and sender address from which you were expecting to receive the email (that never arrived).