Not correct source for transactions
User scenario is simple: Register → Registration Confirmation via email → cash deposit. And here we have a problem that transactions are recorded at the transition from the email, but not on our advertising sources. And spoil our ROI.
What we should do that our transactions recorded to correct sources?
Re: Not correct source for transactions
If i understand true, you lost your traffic source on Registration mail right? Visitors click your link in your email and so you see all transaction came from email.
If so, i guess "Removing referral traffic sources" is work for you. You can read details here https://support.google.com/analytics/answer/2795830?hl=en
By default, a referral automatically triggers a new session. When you exclude a referral source, traffic that arrives to your site from the excluded domain doesn’t trigger a new session. And this session recorded previous sources.
This feature is only available for Universal Analytics and dont forget if you do that, you exclude all traffic from this email server domain.
I used it in a website who use Third party payment systems and its work. You can test too i think.