Most email marketing clients will, at some point during managing their campaigns, notice that they’re emails at times reach their subscribers’ inboxes faster or slower than with a previous send. So a question we hear quite often is: “How long will it take for my newsletter to be delivered?”
To answer this question, we picked the brains of our delivery expert, Shaun Swanepoel. “We can only deliver as fast as the recipient servers allow us. If there was no limit, there would be no strain caused by retrying a mail and we would deliver REALLY INSANELY fast if given addresses are valid, there are no network issues at the recipient side and mailboxes are not full.”
See, when sending emails, they go through numerous stations. In past blog articles we’ve said that, in this regard, it’s very similar to traditional mail. Because of this process, there are a number of things that may affect your campaign’s delivery time. To name a few:
• How busy the Internet Service Provider (ISP) is
• How fast the receiving mail server will accept it
• Anti-spamming techniques the receiving server may implement to ensure that SPAM does not get through to the recipient.
How busy the ISP is

Just like any other service, certain times of the day, month or year are busier than others for ISPs. There are times (for instance during the festive period or at certain times during a normal working day) that are busier than others – and it is at these times, when the ISPs web traffic is at its busiest, that email sends may be delayed. It’s a good idea to keep this in mind when planning your campaigns.
How fast the receiving mail server will accept the incoming send
Each email is sent from a sending server to a receiving server. However it’s not just a matter of getting to the other end. With SPAM being everyone’s pet peeve, ISPs are taking great pains to try and ensure that their users don’t have to put up with a million SPAM emails in their inboxes, so the set up certain specifications that every email needs to go through if it wants to be delivered to the inboxes of that ISPs clients. These settings vary from ISP to ISP, but will generally include some sort of limit on the number of recipients per message or connection; or a rate limit, i.e. a limit on the number of messages you can send in a certain period of time. Basically, it’s an outline of how many emails they are willing to accept at any given time.
If your sends don’t comply with these specifications, the emails will probably bounce. Not to worry though, bulk email service providers enlist the help of Mail Transfer Agents (MTAs) to arrange their sends according to the varying limitations of the different ISPs, ensuring that their sends comply with these regulations.
Anti-spamming safety measures
There are a wide range of anti-spamming strategies implemented by ISPs. (Shaun suggested you read more about them here.) A common example is grey-listing, when emails are required to retry for a certain specified time period before the ISP will accept them. This is an effective anti-spamming device, because spammers generally won’t bother retrying to send their message. However, it does of course mean that your legitimate bulk email sends will also take a while before they are delivered.
So you can see, predicting anexact delivery time is a technical business – and near impossible to do as there are so many factors that can cause a delay in your send. GraphicMail tries to ensure timely delivery: We’re a member of ReturnPath, the EEC and Truste. To find out more about deliverability issues, read another blog article or watch our video.