I am delivering email newsletters since 2012 using different kind of services.
I am familiar with Interspire, Mailwizz, Sendblaster and etc.
I've tested all well known ESPs like Mailjet, Sengrid, Mailerlite, Active Campaign, Aweber, Mailgun and etc.
I have experience how to deliver your emails into customers inboxes (especially gmail!). Like you probably noticed good mailing provider is not enough if you want to reach good inbox rate in emails delivery, I can share my knowledge with you and help you to solve all delivery issues. ;)
Thanks!
Domas