As part of the best practices of opting in to newsletters and deals, you should require that everyone confirm their email address. To do this you need to send a confirmation email to the person after they sign up. Most paid email services take care of this process automatically for you as per of the newsletter signup form that you would add to your home page.
If you don't pay a service, you shouldn't simply capture an email address through your website and start sending special offers, you still need to send a confirmation email. You do this simply by manually sending an email out to the customer and having them reply. That's a lot of work, which is why you should just pay a monthly service to do it for you.
Many customers will type their email address wrong, or they simply do not understand the correct format of their email address. Just this week we were providing tech support for someone who swore his email address was john@firstname.lastname@example.org. He really believed that his email address had 2 @ symbols.
If you don't confirm new signups you could wind up with many bounced or undeliverable emails the next time you send your newsletter. Many automated email systems will watch the number of bounced emails you have. A high percentage of bounced emails usually means spamming and you will eventually get yourself blacklisted.
The important part of this signup process is that the customer needs to put your sending address on their white list. After they give you their email address you should give them a message saying "We just sent you a confirmation email from email@example.com. Please add that email address to your white list and check your spam folder."
After they confirm their email address don't change your sending email address, confirmation email, thank you/welcome email, newsletter@, info@. If you tell people to check their spam filter to confirm, they will.
If they put your email address on an email whitelist it will not get filtered. So don't change your email address from the confirmation email to something else. A few of the jewelers we track changed from the owner's name in the thank you, to info@ and then to news@. There was no warning and no chance to adjust the spam filter.
On the other hand, most retail jewelers will never change their newsletter email address, but a lot of retailers are using their personal email address instead of an info@ or newsletters@ account.
Whatever you do, just keep your email address the same from the moment someone signs up for your newsletter and you will reduce the likelihood of spam filtering.