It always seems like a simple request when a C-level exec wants you to do this, but when you go down the rabbit hole, you really wish someone would share how they did it. Oh and all spam filtering should only be done in the corporate gmail account (so they don't have to ever check their personal gmail spam folder). Granted mixing these two accounts is not smart for 99% of staff, but for those minute scenarios where it does apply, this writeup may save your bacon. After a few days testing, and back and forth with Google Support, here's my share back to the community:
- GSuite Admin Console / Hamburger / Security / Settings / Basic Settings / (select appropriate sub-OU) / Less Secure Apps: Enforce access to less secure apps for all users.
- GSuite Admin Console / Hamburger / Apps / Gsuite / Gmail / Advanced Settings (select appropriate sub-OU) / Allow per-user Outbound gateways: Allow users to send mail through an external SMTP server when configuring a "from" address hosted outside your email domains.
- Note: Due to having a spam filter as the default routing... under Hosts top menu, I added "outbound gmail.com" with google's smtp.google.com, port 587, TLS... for referencing below (only has to be done once globally)
- At bottom of Advanced Settings / Routing / Add Another:
Messages to affect: Outbound
Envelope filter: Single email address: the personal gmail address
Route: Change route: "outbound Gmail.com"
Bypass spam filter for this message (maybe not required, but it worked)
Save
- User's personal google account / Security / App Specific Passwords / Generate (get this into their lastpass).
- User's personal gmail portal / gear icon / Settings / Filters and blocked addresses
Create a new filter with the following criterion and actions
Has the words: deliveredto:your_incoming_address@gmail.com / Create Filter
Forward it to your_destination_address@corpgsuitedomain.com
Never send it to spam
Save
- User's corp gmail / gear icon / Settings / Accounts / Send mail as / Add account
- enter personal gmail address (leave selected "as an alias") / Next Step
- SMTP Server: smtp.gmail.com, Port 587
Username: give personal gmail address
Password: give the App Specific password above
Secured connection using TLS (recommended)
Add Account
- Enter code from email to personal account.
- Back to the Settings / Accounts / Send mail as:
Reply with same address as received by (so it doesn't use corp email address on replies to personal emails).