Why the delivery of my emails is delayed?

Simple Hosting is using so-called greylisting against spam.

What is greylisting?

Greylisting is one method of defending email users against spam. Using greylisting will temporarily reject any email from a sender it does not recognize. Basis for a server employing greylisting typically are three pieces of data for each incoming mail message:

  • The envelope sender address
  • The envelope recipient address
  • The IP address of the connecting host

This data is registered on the mail server's internal database and the email will be dismissed until the configured period of time is elapsed.

A classical example of a greylisted email that is reviewed by Simple Hosting’s antispam servers is: 

  • The senders’ address hans.sample(at) is sending an email for the first time to a recipient address configured on our mail servers.
  • The senders’ address does not correspond to the reply email address. For example, receiving an email from hans.sample(at) and juerg.meier(at) is entered as the reply email address.
  • The senders’ address is hans.sample(at), however, the mail was sent over a mail server from The mail server should be bluewin to be correct.
  • The senders’ address is hans.sample(at) and was sent over a mail server Again the mail is suspected spam, as spammers are not sending junk mails over an own official mail server.

The temporary rejection is issue of the SMTP protocol (RFC 821) and means that the mail service degrades over a short period of time. If the mail is legitimate the originating server will try again after a delay, and if sufficient time has elapsed the email will be accepted.

Validity of emails subjected to greylisting

The data registered on the mail server's internal database, consisting of the sender- and recipient address and the IP address of the connecting host, are stored at the anti-spam servers for max. 160h. The entry is deleted if no further email from the sender address is incoming during this time.

Why greylisting?

Greylisting is particularly effective in many cases at weeding out misconfigured mail servers, and is gaining in popularity as a very effective anti-spam tool. It also increases the chances of spam sending worms' long standing connections and Trojans to be noticed. The disadvantage is that mail from unrecognized servers is typically delayed by about 15 to 30 minutes.

Deactivating greylisting?

Simple Hosting can provide exception lists for single sender- and recipient addresses or a whole sender domain. Increased spam messages not subject to above-mentioned criteria are the consequence. Please send us a support ticket with all your information.