Why does search in Google Mail not find some substrings but others work?

Question

Today I saw a very strange behavior when searching in Google Mail. I was looking for an eMail which contained an IP: 192.168.100.150.

I couldn't remember exactly what it was, but I knew the first three parts, so I was searching for 192.168.100 and did not get any results.

After several tries, I tested 192.168 and and suddenly got several results, including the IP I was looking for.

The IP is part of a URL like follows: https://192.168.100.150/SOMEPATH/

Summary:

Searching for 192.168.100 did not work.
Searching for 192.168 or 192.168.100.150 worked fine.

Can someone explain this behavior to me?

Answer 1

Because Gmail interprets searches for something, that looks like a number, as a search for that number, and searches for strings as searches for complete words.

Accordingly, your search for '192.168' is interpreted as a search for the number 192 decimal point 168.

And your search for '192.168.100.150' is interpreted as a search for the word '192.168.100.150'.

Because '192.168.100' is not a valid number format, since it has 2 decimal points, it is considered a search for a word, and because (don't ask me why - my best guess would be, that google is indexing exact words and numbers and returns results from that index, and is thus simply not able to actually perform a full-text substring search for that reason) google is not able to search for substrings of words, it does not find your '192.168.100.150'.

This behavior is hinted by the comment on "Search operators you can use with Gmail" (https://support.google.com/mail/answer/7190?hl=en) --> "Note: When using numbers as part of your query, a space or a dash (-) will separate a number while a dot (.) will be a decimal. For example, 01.2047-100 is considered 2 numbers: 01.2047 and 100."