==== external to internal, with extension
|foo+extension@example.com|
|foo bar+extension@example.com|
|foo+ext+extension@example.com|
==== external to internal, without extension
|foo@example.com|
|foo bar@example.com|
|foo+ext@example.com|
==== external to external, with extension
|foo+extension@example.com|
|"foo bar+extension"@example.com|
|foo+ext+extension@example.com|
==== external to external, without extension
|foo@example.com|
|"foo bar"@example.com|
|foo+ext@example.com|
==== internal to internal, with extension
|foo+extension@example.com|
|foo+ext+extension@example.com|
==== internal to internal, without extension
|foo@example.com|
|foo+ext@example.com|