Many of our clients like to use MailChimp (and similar platforms) for their email marketing. Systems like it are typically free (for the basic package), simple and easy to use - this is the main reason why we'd recommend them.
More generally, some clients do encounter difficulties when their platform asks for confirmation of "double opt-in".
Strictly speaking the phrase double opt-in is a bit of a misnomer as the systems that ask for "First-party opt-in" or "Double opt-in" email records are really stating you simply cannot use "purchased data".
(In fact double opt-in data is a bit of a data salesman buzz word! that doesn't mean anything at all - trust me I've heard it all before!)
If you're ever in doubt simply Google "**Your Platform Name** and Purchased Data" - this should provide the answer in their T's and C's
The crux of the issue here is not that your data isn't double opt in... its that you're attempting to use purchased data.
MailChimp along with its cousins (Constant Contact, Campaign Monitor, NewsWeaver, Zoho, Eventbrite - amongst many more) all prohibit the use of purchased data within their own T's and C's.
The main reason behind this is as cheap and cheerful platforms they tend not to segment the IP address that each user account makes use of. Therefore if there is a series of 'poor' campaigns that run, each receiving a high ISP complaint ratio this could damage the performance of other users campaigns.
Naturally purchased data is more volatile (these are cold prospects rather than warm subscribers) and therefore there is likely to be a higher complaint rate.
It is for this reason that most platforms would choose to prohibit the use of purchases data.
But they'll never know its purchased data... I'm sorry, they likely will! Platforms like MailChimp take this seriously to protect their wider user base.
They have sophisticated algorithms in place that look at a ratio of open rate, click rate, ISP complaints, unsubscribes and unsubscribe reason and if they suspect you're misusing the system they'll pause your account or stop your campaigns.
What can I do then? There are a wealth of alternatives out there that are compatible with purchased lists.
If you're experiencing issues please email firstname.lastname@example.org or call on 0161 414 1080 and your consultant would be delighted to assist!