inboxing depends on many things like email size, email bounce, email content, IP reputation, Server Setup, rDNS, DKIM, SPF, Sunject Content, email quantity, emailing speed everything you should maintain. Sometimes you may get emails in spam when you are testing emails because TEST content of Interspire is showing as spam in gmail as well as in Yahoo, So it will land to spam, but when you manage the reputation of your IPs ( It may take 2-3 months to get good reputation of your IPs ). Also Never send emails from forged email ID... Like your domain is xyz.com and you are sending emails from
[email protected] then there are chances that your email land to spam except you have signed dkim for that domain too.
Also You should use multiple Ips for sending emails if your quantity is large. And I would suggest you not to send more than 100 emails per IP to keep your IP active and reputed in Major ISPs like yahoo, gmail, Aol etc...
I saw some guys provide something like 98% inbox or 100% inbox, So I would like to say it's just impossible from anyone, even from Major ESPs can not guarantee you about inboxing... Simple thing, Did you ever got adult content or Viagra emails in your inbox of gmail or yahoo?... almost 100% lands to spam... So no one can guarantee about 100% inboxing but yes, you can improve your inboxing by taking care of some small factors.
I provide email marketing services and I take care of these things and provide setup with multiple
IPs and give them some sending instructions for sending emails and bingo...they are doing very good at emailing....
Let me know if any question.... skype : bmsoftwares