A common question from my Mailchimp clients is how they may avoid any of their email campaign landing in their subscribers spam or junk folders. Unfortunately there is no means of totally removing the chance that the EDMs will land up in a spam folder but the chance can be minimized.
The issue at hand is that there are very many different email spam detection methods and software that organizations use and it isn’t possible to know and address the tens of millions of variations in factors that spam software use. As an example, with Microsoft Exchange Online you can determine various factors that determine what a spam email message contains.
There are three basic ways of minimizing the chance of your email campaigns going to spam/junk:
Custom DKIM/SPF
Follow the Mailchimp instructions for setting up DKIM and SFP records at which will help add authority to your domain. The largest recipient of Mailchimp campaigns is Gmail (including Google Apps) and they are focusing efforts on increasing the use of SPF and DKIM records for email.
Campaign content
The proportion of text to images and links in an email are a signal of quality to spam filters. It is important to include a few paragraphs of plain text in natural language to each campaign and not too many hyperlinks.
Whitelisting
On the receiving server (i.e. not Mailchimp but any recipients server) it will help to whitelist the Mailchimp sending domains and IP addresses. This however entails the recipient adding these details to their incoming spam filter which is very difficult to get done.
The first two items above may be performed by you and will certainly have a positive effect on your deliverability.
Let’s remember Mailchimp actually don’t support custom SPF, they always use their own domains in the sender-envelope.
When they ask you to configure SPF, they should actually be writing SenderId.
More on SPF best practice here: https://www.m3aawg.org/sites/default/files/m3aawg_managing-spf_records-2017-08.pdf