Add SMTP authentication auto-discovery #107

Job	Run time
Test with Codecov coverage (ubuntu-latest / 1.23)	49s
Go vulnerabilities check	20s
Dependency review	10s
golangci-lint (1.23)	28s
REUSE Compliance Check	16s
Test with SonarQube review (ubuntu-latest / 1.23)	39s
Test (macos-latest / 1.19)	38s
Test (macos-latest / 1.20)	26s
Test (macos-latest / 1.21)	22s
Test (macos-latest / 1.22)	22s
Test (macos-latest / 1.23)	19s
Test (ubuntu-latest / 1.19)	28s
Test (ubuntu-latest / 1.20)	36s
Test (ubuntu-latest / 1.22)	22s
Test (ubuntu-latest / 1.21)	25s
Test (ubuntu-latest / 1.23)	27s
Test (windows-latest / 1.19)	22s
Test (windows-latest / 1.20)	23s
Test (windows-latest / 1.21)	23s
Test (windows-latest / 1.22)	21s
Test (windows-latest / 1.23)	21s
Test on FreeBSD 13.4'	2m 14s
Test on FreeBSD 14.0	2m 12s
Test on FreeBSD 14.1	2m 16s
	15m 39s

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