Massive traffic spike to website immediately after email blast

[tarh33l]

We're an agency helping one of our clients with their website implementation.

Over the last week, we've had two instances where a very large spike in traffic has brought down the live site.

After some analysis, we realized that these spikes directly coincided with email blasts being sent to about 90,000 international contacts.

Interestingly, each time these blasts are sent, our client will also send to about 400,000 North America contacts about 6 hours later. For the North America blasts, we do not see the immediate spike in traffic and the site remains up.

Because the spike happens within a minute or so of the emails being sent out, we're certain this is not actual user traffic to the site (we're in the process of trying to isolate the source of the requests).

We're worried that either:

1.) HubSpot is validating embedded links in the email (which point users to the site) and is doing this for each email sent

2.) Email servers in non-North American countries are immediately validating the links in the emails automatically (which results in request back to the site)

Our client has been sending email blasts like this for months and it hasn't been an issue so we're a little stumped why this is suddenly problematic.

Any input we can get on this would be greatly appreciated.

[melrho · Accepted solution]

Hi @tarh33l !

Thanks for reaching out, happy to help here! 

This spike could be related to bot traffic and a good resource to utilize may be this knowledge base article. I'd recommend reviewing your traffic analytics tool to get a better understanding of your traffic sources. 

The following knowledge base articles may be helpful:
Analyze your site traffic with the traffic analytics tool
Understand HubSpot's traffic sources in the traffic analytics tool 

I would recommend connecting with HubSpot Technical Support, as Support is included in your subscription and this spike in traffic may require deep troubleshooting and access to your account. Our Support Team will be able to provide real-time assistance for this matter, where you are able to share screenshots and further information about this.

When contacting technical support, I would recommend including links to the specific emails and screenshots of traffic spikes.

Best, 
Mellissa

[tarh33l]

Thanks Mellissa.

We're fairly certain it's some sort of bot traffic but we can't really figure out why this is happening immediately after sending these emails.

We'll open a support ticket with HubSpot.