Shared IP Pools Overview
Have you ever had a virtual mailing address where you could receive mail at a shared location? This is basically how a shared IP works: you co-locate your mail streams with several other senders. This article will provide an overview explanation of Twilio SendGrid’s Shared IP pools used under the Trial and Essentials plans.
How does it work?
When sending email through an account that is under the Trial or Essentials pricing package, your account will be utilizing a shared IP pool. A shared IP pool is a group of IPs that are bundled together and used to send mail equally.
Being grouped with others on a list of IPs can offer several benefits. First, these plans are our most affordable tiers, and allow for a lower cost way to scale beyond 100 emails a day. Second, volume will have less of an impact on send quality since other clients are sending as well, so the IPs are already warmed. This way you can start sending out a blast of emails immediately.
With those benefits in mind, there are some additional things to consider when looking at shared pools, such as email reputation. Email reputation is based on the authentication records and sending volume/history. Because the IPs are shared, IP reputation will also be shared amongst senders. You are sharing IPs with hundred, sometimes thousands, of Twilio SendGrid users and the sending habits of others can affect your sending.
This is the major drawback to share pools -- the lack of control over IP reputation. Although your domain will be yours, sending activity from the shared IPs may be impacted by sending from other users. We group these pools based on sending activity and metrics, so you can ensure you are kept with good company by following best practices; this also helps mitigate any delivery impact from other senders as long as you are keeping with best practices and sender guidelines.
If you send transactional emails, there are some differences when using shared IPs that should be taken into account. Shared IPs are poorly suited to sending transactional type messages (opt-in confirmations, password resets, receipts) for two reasons:
1. Marketing mail (the primary type of mail sent by other shared IP pool users) inherently lowers IP reputation.
2. Transactional type messages have the lowest tolerance to risk, which use of shared IPs has in abundance, by nature of being shared among senders.
Twilio SendGrid has an automated IP pool system to dynamically and responsively sort users based on their engagement quality. Meaning, if you improve your sending habits to optimize engagement quality, you will automatically advance to sit adjacent to more performant senders within 24 hours. It also means if there is a sender in your pool that starts to underperform, within a day they will be automatically transitioned to a different pool, insulating your email program from risk.
What to do if my IPs are blocklisted?
IPs being listed on blocklisting services is a common issue that occurs in any email sending program. This is increased when you have many accounts using these shared IPs.
Not all blocklist is created equal, and not all blocklists cause delivery issues for all accounts. Reputation is based on IP and domain, if you have a good sending history with the recipient server you may not see as much of an impact. Some blocklists are not widely used by recipient servers, and those will not typically cause an impact either.
The first step is to see if you are seeing bounces that reference the blocklist. When delivering mail one of the possible responses is a bounce, which indicates a rejection. With these bounces usually comes a reason, which indicates the problem that caused the failure. With a bounce due to blocklist, typically it will advise the blocklist and a URL that can be visited for more details or to delist.
Procedures for how and when an IP is blocked can vary. Some blocklists will only automatically delist IPs after a certain time, others require an active reach out. Our delivery team is always working to monitor pools and deal with any problematic senders if they exist, as well as work on getting IPs delisted. Despite this, sometimes just as quickly as we act to delist an IP it is relisted again. In addition, blocklisting services such as Spamcop do not allow manual delisting, and so we have to wait for an automatic 24-48 hour turnover to see if the IP has been mitigated.
If you are using a shared pool and you are seeing bounces that reference a blocklist, we would encourage you to reach out so that we can investigate further: Deny Lists.
Can I move to a different pool?
Twilio SendGrid is unable to move IPs in and out of pools because it gives the impression of Snowshoe Spamming: a strategy where spam is propagated over several domains and IP addresses to weaken reputation metrics and avoid filters, which can make things worse. But our systems will programmatically move accounts to different pools based on reputation and internal logic, based on sending history and metrics:
- Engagement recency: are you sending email to recipients who have recently opened or clicked?
- Unique open rate: are your recipients opening your messages at a healthy rate?
- Spam rate: are your messages generating excessive spam complaints from your recipients?
- Bounce rate: are you attempting to send too many messages to addresses that don’t exist?
- Bounce classification: are mailbox providers rejecting your messages due to a poor sender reputation or spammy email content?
It means that Twilio SendGrid has automated the IP pool system to dynamically and responsively sort users based on their engagement quality. So, your sending habits will be used to optimize engagement quality, and you will automatically advance to sit adjacent to more performant customers within 24 hours. It also means if there is a sender in your pool that starts to underperform, within a day they will be automatically transitioned to a different pool, insulating your email program from risk. Maximize Deliverability Control with Shared IP Address Pool Improvements
Also, our delivery team proactively monitors our shared IP pools and attempts to mitigate all blocklisted IP's as soon as possible. Despite this, sometimes just as quickly as we act to delist an IP it is relisted again. We encourage you to reach out if you have questions about your specific sending. Delivery issues can vary widely, and looking at the specifics is the best way to find the issue and any resolution.
What to do if I’m sending critical emails?
Twilio SendGrid’s Shared IP pools are an excellent low cost way to send mail to clients without worrying about volume and warmup. By following best practices and growing the email program overtime it is possible to see good delivery. However shared IP pools do have a higher deliverability risk than dedicated IPs.
If you’re sending critical email that cannot be influenced by external factors outside your control such as these block listings, we would recommend using a Dedicated IP. The only practical solution to ensure a better deliverability of your emails and to avoid unforeseen blocklistings is to use your own dedicated IP address. Since nobody else sends from the IP, you have full control over the reputation and are able to proactively mitigate delivery problems as opposed to relying on Twilio SendGrid’s Shared IP pools. This gives you, as a sender, full control over your sending. Upgrade or Change your SendGrid pricing plan.
The dedicated IP combined with a proper warm-up and sender authentication can lead to better and more consistent overall deliverability. IP warmup involves gradually increasing your sending day by day on a new IP. The slower you can warm up the better. Warm up to establish a solid and positive IP reputation. Recipient servers view IPs with no sending reputation almost as negatively as IPs that have a bad sending reputation. Also, you will be able to set up a rDNS. Setting up reverse DNS on an IP address allows mailbox providers to verify the sender when they do a reverse DNS lookup upon receipt of the emails you send.
If you don't want to upgrade another strategy known to be an effective mitigation technique when dealing with rejections from smaller providers, is to reach out to the network administrators for the domains blocking your mail to see if they are able to whitelist your sending domain (most often reached at postmaster@domain.com). This will be a viable strategy for smaller email providers.
Shared IP Pools still offer an excellent cost saving option that can work well for new email programs or programs that need more flexibility on volume. Delivery challenges exist for each type of sending style, and good delivery can be seen with each. As with any issue, we encourage you to reach out if you have any questions about which plan type is best for you