The automatic syncing of emails to Salesforce is great, and seamless when paired with G-suite Mail. I'm a huge fan of their notification tool too to bubble up specific threads at any specified time.
What we liked about it was its simplicity once set-up, and the ease of telling whether or not someone opened the email sent, and where that person was located.
Yesware's mailmerge and templates are some of the best in the industry in terms of ease of use and overall function.
Their layout within their templates are completely restricted. This means you cannot upload anything from a photo to a gif without some type error or layout dysfunction.
Spam detection software is junk. We have found no spam detection software that is reliable and turn off anything to ensure nothing is missed.
The emails I sent using yesware tracking were send to spam. Which makes it's use redundant if the tracking send with the emails can be easily tracked and qualified as spam.