If you have a hosting package with us and receive emails via it, there may be occasional delays in receiving emails. The cause is the SPAM protection greylisting.
This affects e-mail addresses from which you receive an email to your recipient address for the first time.
When receiving an email, greylisting checks whether the sender is sending an email for the first time. If this is the case, the sending mail server is told to retransmit the email in 5 minutes at the earliest. If the email has been delivered after this time, this email address will be whitelisted in the future and emails from the sender will be delivered without this delay in the future.
SPAM senders do not normally perform the redelivery because of the high effort and resource requirements involved. This is an effective way to combat SPAM.
You can disable greylisting if necessary. This is done in the Froxlor administration interface. There you can edit an existing email address with the pencil icon and disable greylisting. Note that this could result in more SPAM messages being delivered in the future.
More information about greylisting can also be found on Wikipedia at:
https://en.wikipedia.org/wiki/Greylisting_(email)