Last week, SendGrid’s email experts Elmer Thomas and Carly Brantz broke down some tips and tricks to make sure your emails don’t get banished to the spam folder. There were so many great questions during the webinar that we weren’t able to get to. In an effort to keep the conversation going, Carly and Elmer took some time to respond to these questions here.

If you missed the webinar, you can access a recording here.

How helpful/important is it to be certified by Return Path?
CB: Return Path Certification is the most widely accepted “whitelist” program for permission-based email senders. A whitelist is a list of email address or domain names from which an email blocking program or ISP will allow messages. For senders who appear on a whitelist that is used by the most important ISPs, the chances of making it to the inbox dramatically increase. The certification program has deep corporate and consumer market coverage and lets certified senders improve email deliverability rates at more than 2 billion mailboxes worldwide.

I would love to know more about testing for heuristics. We are doing a few things on our end, but are still getting messages bounced due to content even though our tests come out clean.
ET: Try sending your emails through a SPAM checker and analyzing the results. There are a few to start with:

Use the keyword phrase “spam checker tool” if you don’t like the above tools or are looking for more resources. For general knowledge about heuristics, Wikipedia has a good explanation (be sure to check out the References section).

Do you have any examples of authenticating email?
CB: Best practice is to implement the three most accepted methods of authentication. You can find specific examples of each at:

Are inbox rates affected if I change the “from” email address based on the type of product we are promoting?
CB: Email addresses can be divided into two parts, the “Friendly From” and the routable part. For example, “Franklin Fasteners” <>. We don’t think you’ll incur a reputation hit if you change the “Friendly From” part (e.g. “Franklin Fasteners”) but you are more likely to incur a reputation hit if you change the routable part. Not all system use the “from” address for reputation, but some do. They are more likely to associate your sending reputation to your IP or your DKIM signature (inserted into your message headers) or a combination of both.

If the reply-to in the header is to a different domain, does that automatically make it seem deceptive? We send emails to groups of people and use the email of the group captain as the reply-to header.
ET: No. The SMTP RFC specifically allows for this functionality. Note that a minority of admins may disregard this rule and impose their own rules regarding from/to mis-matches.

Is there a list of Phishing Phrases and Trigger words somewhere?
ET: Here are some resources that should help with phishing phrases and trigger words that should be avoided within e-mail content”

How does inbox behavior work in spam filtering?
CB: ISPs use various types of inbox behavior in spam filtering.  Some track the time the email stays in the inbox before it is deleted or how often the subscriber interacts with the mail.  All track who marks your messages as spam by clicking the “this is spam button” and some use panel data from real subscribers who are asked to verify the appropriateness of inbox or spam folder placement.

What about using CSS styles in-line? (In regards to using CSS in email content).
CB: We recommend using inline CSS.  CSS provides ease and flexibility however the support varies among email clients. Some strip it out entirely.  It is extremely important not to use external CSS like that which is in a file like a website does.  Instead embed it in the email or inline written at the very least.

Our permission based subscribers are getting regularly throttled by Comcast. Comcast tells us the IP is not on a blacklist. Is Comcast just the devil, or is something else going on here?
ET: Comcast uses SenderScore to determine when to throttle incoming email per RL000001. You may check your SenderScore here.

We have been collecting contacts for years. If we move to SendGrid, will our list have to opt-in again?
CB: If you have a list of opted in subscribers we do provide the option to upload those lists to our system easily and mail to them from SendGrid.

How do you find your IP address, like you mentioned, it’s not always the web server IP.
CB: Every device connected to the public Internet is assigned a unique number known as an Internet Protocol (IP) address. IP addresses consist of four numbers separated by periods (also called a ‘dotted-quad’) and look something like You can find your’s by visiting

Do you have any newsletter templates that will ensure good delivery?
ET: You can not ensure good delivery with a template. There are many factors that go into achieving good deliverability. I suggest you take a look at our Email Deliverability Guide for further details.

I have a virtual assistant located overseas and she sends my marketing campaigns for me using SendGrid. Would her IP address affect our reputation?
ET: No, because we do the actual sending of your email in that case.

What is the role of email source ip address in email delivery?
ET: The source IP address has a reputation attached to it. We recently had a webinar on this topic, check out this link for a recording, followed by Q&A.

My customer wants to buy an email list, is it legal to send it, or is it pure spam?
CB: While it is not illegal to send to an email lists, our opinion at SendGrid is that mailing to a purchased list is never a good idea.  Reputation is key to your email delivery and a huge part of that is maintaining the best permission practices you can.  Make sure that your subscribers want to receive the email you are sending and that they are expecting the email.  An easy way to increase complaints is to purchase a list and send to people who not only do not know who you are but why they are getting email from you because they never gave you permission to send.  SendGrid does not allow our customers to mail to third party lists through our infrastructure.

Do you suggest to use your SMTP server as our employee SMTP server?
ET: Yes, as long as you comply with our terms of service.

We are doing double opt in, and our database is conformed by people that invite their families and friends. That means that we have almost no SPAM. We are doing everything you talked about, but still get complaints on our contacts that they are not receiving mails, and we have to tell them to look at their SPAM inbox… How come businesses like Groupon get away with all these policies, when they buy mailing lists or don’t have the double opt-in.
CB: In my opinion it comes down to relevancy.  Companies that are sending relevant content that subscribers want like a killer daily deal often can get away with it because people want those emails.  Email delivery is a science and there are many steps involved to getting your email delivered.  You need to warm up your IP addresses and take precaution to send relevant content that your subscribers are expecting.

How bad is it to hit a spam trap?
CB: Having spam traps on your email list can cause plenty of problems.  Sometimes spam traps are added accidentally by entering a typo and adding an email address by mistake.  The primary way is by using a third party list that had them included.  Once you hit one it is difficult to remove them because the ISPs don’t want to tell you which address is the spam trap.  The best way to avoid them and remove them is verifying that your list is clean and your subscribers have opted in to receive email from you.

If you purchase a list, can you check with the vendor of the purchase list if their emails are free of spam traps, are they legally allowed to release that information?
CB: It is impossible to know if there is a spam trap on their list or not, that is a primary reason we advise our clients NOT to send to a purchased list.  A spam trap is an email address that doesn’t send email but identifies spammers who send it email.  They are created by the ISPs to trick senders so there is no way to know except by having permission to send to your subscribers.

Our contacts subscribe freely and the double-opt mail goes to the SPAM box… how will they confirm if they don’t get the mail???
ET: This is one reason why people choose to use a service such as SendGrid. If you choose to utilize your own email system, these tips in our Email Deliverability Guide should help you.

I’m screwed maybe? My list was hosted with GetResponse. The IP that I’m on hit 28 spam traps.
CB: You are definitely not in an ideal situation!  I would advise that you not send to that list because identifying which addresses are the spam traps is extremely difficult.  You will need to rebuild your list or work on doing a “reactivation” campaign to ensure that the addresses on your list are legitimate.

Does SendGrid provide sender id setup? When I look at the header in hotmail sender id comes out NONE or Fail.
ET: No, we do not.

Does Sendgrid allow to send to purchased lists?
CB: No, we do not.

As SendGrid's Senior Marketing Analyst, Danny is responsible for keeping the marketing team focused on making data-driven decisions to help make sure we are providing value for our customers and prospects. While he may spend his days knee deep in spreadsheets now, Danny spent most of the last 10 years managing email campaigns, website optimization, and PPC campaigns for B2B companies.