^start of line
\[the literal [ (9110 / 1338 / 5B16)
\S+any non-whitespace character, repeated at least once
\s+any whitespace character, repeated at least once
Group 1(\d{1,2}\.\d{2}\.\d{4}) \d{1,2}a digit, repeated between 1 and 2 times
\.the literal . (4610 / 568 / 2E16)
\d{2}a digit, repeated exactly 2 times
\.the literal . (4610 / 568 / 2E16)
\d{4}a digit, repeated exactly 4 times
\s+any whitespace character, repeated at least once
Non-Capturing Group(?:\d{2}:){2} {2}repeats the group contents below exactly 2 times:
\d{2}a digit, repeated exactly 2 times
:the literal : (5810 / 728 / 3A16)
\d{2}a digit, repeated exactly 2 times
\s+any whitespace character, repeated at least once
SMTPthe literal text SMTP (case sensitive) \s+any whitespace character, repeated at least once
Server:the literal text Server: (case sensitive) \s*any whitespace character, repeated any number of times
Non-Capturing Group(?:\S+\s*\()? ?repeats the group contents below at most once:
\S+any non-whitespace character, repeated at least once
\s*any whitespace character, repeated any number of times
\(the literal ( (4010 / 508 / 2816)
Non-Capturing Group(?:\d+\.){3} {3}repeats the group contents below exactly 3 times:
\d+a digit, repeated at least once
\.the literal . (4610 / 568 / 2E16)
\d+a digit, repeated at least once
\)?optionally matches the literal ) (4110 / 518 / 2916)
\s+any whitespace character, repeated at least once
+matches at least one character from the set below:
\wany word character
.the literal . (4610 / 568 / 2E16)
-the literal - (4510 / 558 / 2D16)
\s+any whitespace character, repeated at least once
\d+a digit, repeated at least once
Negated Character Class[^\n]* *matches any number of characters outside the set below:
\na line-feed (newline) character (ASCII 10)
$end of line
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string