Update postgrey whitelist

[casperklein]

Description

Similar to the problem that mail in a box had, the included /etc/postgrey/whitelist_clients is outdated by years, the last entry is from 2015. The official current version can be found at http://postgrey.schweikert.ch/pub/postgrey_whitelist_clients

Even the upcoming Debian 11 will not include an updated whitelist, so this should be merged.

Fixes #2040

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (non-breaking change that does improve existing functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md or the documentation under docs/)
• If necessary I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[dfyx]

That was quick, thanks a lot!

[frugan-dev]

FYI postgrey_whitelist_clients has been updated recently https://github.com/schweikert/postgrey/commits/master

[casperklein]

It's already included in the current :edge build and will be in the next release automatically.