I am adding different email address in reply_to instead of using same as in from option. Here is how I set reply to..
$this->email->reply_to('example@gmail.com', 'Any Name');
But setting reply_to email results in Email to go in promotional tab of gmail instead of primary tab.
If I don't use reply_to, only then email goes in primary tab. Is there a way to save email in primary tab while keeping different email address for replay_to?
That is the purpose of reply-to -- to offer an alternate reply address, which gmail correctly identifies as a marketing email. Though that's not the only reason they might flag your email as a promotion. Trying to outsmart their algorithm is probably not your best bet.
There are some strategies to help ensure your emails get to the primary tab, one of which is making the reply-to the same as the from. Requesting that your recipients white-list your reply-to domain is also one way.
https://www.convinceandconvert.com/email/how-to-ensure-emails-gmail-primary-tab/
https://www.websiteplanet.com/blog/11-ways-keep-emails-gmails-promotions-tab/