Hi Jordan,
Are you using Google Apps for Work to have Gmail accounts with custom email addresses (not ending in @gmail.com)?
If so, here’s a couple things that might help:
1) Don’t use an alias address. If your primary email account is johnsmith@convertmedia.com, you may have aliases setup for js@convertmedia.com, jsmith@convermedia.com, and johns@convertmedia.com. Using one of those alias accounts will not work.
2) Don’t use a group email address. If you have an email like info@convertmedia.com that goes to a group of people, you will not be able to enter a unique password for that account because Google’s SMTP server requires authentication. The password for the group owner won’t work either. So, you will need to have a dedicated email address like website@convertmedia.com with it’s own password.
Note: If you use this method with a dedicated website email address, make sure to set the “reply-to” to be the user’s name/email and the “from” to be something like ConvertMedia Website <website@convertmedia.com>. Otherwise you may end up with emails from something like Mary Smith <website@contactmedia.com>.
Also, I’d recommend turning on the vacation notification (in Gmail Settings > General) with a default response letting people know the account is only used for sending emails from the site. This canned response could have contact information listed for company departments.
3) Check to see that you’re allowing non-Google apps to use sign-in technology. To do this in Gmail click on the account icon on the top right corner of the screen (circle shape with a letter or image) > My Account > Account Overview (under Personal info & privacy) > Connected apps & sites (under Sign-in & security) > Allow Less Secure Apps > Turn on. Warning: you will want to use some type of Quiz or reCaptcha when you do this to prevent bots from sending spam from your contact form.
Hope this helps. Cheers!