ESP (email service providers) use a system called spam scoring. In essence, every email that ends up on their servers is sent through an algorithm. That algorithm looks for spam warnings (see below) and scores every email based on them. If an email's total score is above the threshold, the email is sent to the receiver's spam folder.
So what does the spam scoring algorithm take into consideration? It's hard to say since they evolve all the time. All the major ESPs use machine learning to keep on top of spam (which is a big threat to their business). But we know a lot about the general preferences of spam scoring algorithms.
The most important factor in spam scoring is audience engagement. If you send a lot of emails that aren't opened, that aren't read, or that are trashed, your emails will have poor engagement. That's why it's so important to choose your audience carefully. Basically, every email you send that your receiver doesn't engage with, makes the risk higher for your next email being flagged as spam.
If a user actively marks your email as spam, that's a big factor in the scoring algorithms too. It will for sure make it harder for you to reach that specific receiver, but it will also make it harder to get through to anyone else. Again, it's really important to choose your audience carefully and to send them content that they want.
Your ESP has sent spam before
It's not only what you do, but also the reputation of the ESP that you use. If someone has sent a lot of spam from the same email server (IP address), that will hurt you as well.
What you put in the email also makes a difference of course. Some things that will increase your spam score are:
High image to text ratio. If your email contains mostly images, that's a red flag for spam scorers. They can't analyze images properly, so they don't like them.
High link to text ratio. If you include a lot of links in your email you will be punished
Spam trigger words. You can all guess what these are. If not, open your spam folder and find the common words 😄
Full URLs or URL shorteners. Full URLs (ie https://vaam.io/share/12345) will increase your spam score. Spammers are lazy and often don't bother to make proper links. So a "See my vaam" link will perform better than the full URL.
We do what we can to avoid your vaams end up in the spam folder. For instance, making sure that the gifs that we produce aren't too big, that the link is a proper one, and that the server behind the link gives a proper response if queried by an algorithm.
Still, if you send an email with nothing but a vaam gif, your likelihood of being flagged as spam increases. One thing you can do to reduce the risk is to include text content in your email. Again, spammers are lazy so a thoughtfully crafted email with both HTML and text will make spam scorers like you more.
What to do?
Make sure that you select your audience carefully.
Send good content. You need to think about the image-to-text ratio and the link-to-text ratio. You should avoid full URLs and spam trigger words, and you should include a text version of your email.
If you rely a lot on email (and send it from your own domain), you should also consider adding SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). They are technical ways of verifying that the sender is trustworthy, and it will make spambots much less likely to flag your emails as spam.
Subject: Martin <> Vaam
[Name of your prospect] <> [Your Company]
(Feels like you have something related to your company)
Why you are reaching out
What do you offer / can help them with
"Sounds interesting? Please see my vaam below."
Paste the gif at the bottom