# Does capitalization in E-mail addresses matter at all? **URL:** \ **Category:** Factual Questions\ **Created:** [November 21, 2002, 4:28pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961 "2002-11-21T16:28:25Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [November 21, 2002, 4:28pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/1 "2002-11-21T16:28:25Z")
I know it makes a difference in URLs, but I always thought that capitalization was irrelevant as far as E-mail addresses were concerned (i.e., “[toadspittlemail@straightdope.com](mailto:toadspittlemail@straightdope.com)” = “[ToadSpittleMAIL@straightdope.com](mailto:ToadSpittleMAIL@straightdope.com)”). Am I right or wrong? ---
**Author:** ![erislover](https://avatars.discourse-cdn.com/v4/letter/e/71e660/32.png) [@erislover](https://boards.straightdope.com/u/erislover)\ **Post date:** [November 21, 2002, 4:52pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/2 "2002-11-21T16:52:36Z")
I have never seen capitalization matter whatsoever. But for all I know there might be some crazy email system somewhere that is case sensitive. I don’t see anything in the [SMTP](http://www.imc.org/rfc1869) which requires case-insensitive treatment, nor in [POP3](http://www.faqs.org/rfcs/rfc1081.html). So, I suppose it is possible. ---
**Author:** ![dantheman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dantheman/32/9421_2.png) [@dantheman](https://boards.straightdope.com/u/dantheman)\ **Post date:** [November 21, 2002, 5:14pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/3 "2002-11-21T17:14:04Z")
I just sent two emails to one of my other email addresses, one with the first letter capped (“D”), and one with the first letter uncapped (“d”). Both arrived at the same email address. The email was an Earthlink address. So it’s not case sensitive for them, at any rate. ---
**Author:** ![Futile\_Gesture](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@Futile\_Gesture](https://boards.straightdope.com/u/Futile_Gesture)\ **Post date:** [November 21, 2002, 5:35pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/4 "2002-11-21T17:35:22Z")
> [@](#): > > \*Originally posted by toadspittle \* > \*\*Am I right or wrong? \*\* You are right. It makes no difference. The fact it matters in URLs is a touchy subject and relates to Unix file systems. IMHO case sensitivity in most computer related things totally pointless, unintuative and a constant pain in the neck for programmers and web delvelopers everywhere. ---
**Author:** ![Futile\_Gesture](https://avatars.discourse-cdn.com/v4/letter/f/f05b48/32.png) [@Futile\_Gesture](https://boards.straightdope.com/u/Futile_Gesture)\ **Post date:** [November 21, 2002, 5:39pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/5 "2002-11-21T17:39:38Z")
> [@](#): > > \*Originally posted by Futile Gesture \* > \*\*IMHO case sensitivity in most computer related things totally pointless, unintuative and a constant pain in the neck for programmers and web delvelopers everywhere. \*\* Sheesh! :smack: Grammer and spelling, however, is a **good** thing. Case sensitivity in most computer related things **is** totally pointless, unintuative and a constant pain in the neck for programmers and web **developers** everywhere. ---
**Author:** ![erislover](https://avatars.discourse-cdn.com/v4/letter/e/71e660/32.png) [@erislover](https://boards.straightdope.com/u/erislover)\ **Post date:** [November 21, 2002, 5:43pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/6 "2002-11-21T17:43:42Z")
But where would I go to find out that it is pointless, **Futile Gesture**? I thought it was for sure, but I couldn’t find a thing to support the statement. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 21, 2002, 5:46pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/7 "2002-11-21T17:46:12Z")
The old original Internet RFCs for domain names (“[www.straightdope.com](http://www.straightdope.com)”) is case insensitive. Ditto when email names were added. As for URLS, the domain name prefix is case insensitive, while the trailing directory/file/script name may or may not be depending on the file system of the server. (Unix is case sensitive, MS-Windows isn’t. The latter causes huge headaches, not the former.) ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [November 21, 2002, 6:13pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/8 "2002-11-21T18:13:41Z")
ftg why do you say the case insensitivity causes problems? ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [November 21, 2002, 6:15pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/9 "2002-11-21T18:15:56Z")
There is a point, of course: 1. Greater number of options when programming. Thus in UNIX, a command letter R and an r could mean two different things. 2. Better security. If passwords are case-sensitive, it allows the user to capitalize random letters to make them harder to guess. Of course, to the casual user, these aren’t all that important. But a lot of software (especially on old mainframes) is designed for the programmer’s convenience, not the users. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [November 21, 2002, 8:32pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/10 "2002-11-21T20:32:18Z")
> [@](#): > > \*Originally posted by Futile Gesture \* > \*\*Sheesh! :smack: Grammer and spelling, however, is a **good** thing. > > Case sensitivity in most computer related things **is** totally pointless, unintuative and a constant pain in the neck for programmers and web **developers** everywhere. \*\* Well, as long as you’re going to flagellate yourself, I’ll help. 🙂 Sheesh! :smack: **Grammar** and spelling, however, **are** good thing **s**. Case sensitivity in most computer related things is totally pointless, **unintuitive** and a constant pain in the neck for programmers and web developers everywhere. Anyway, I have always bemoaned case-sensitivity but I’ve used Unix so long I’m sort of used to it and it seems almost normal to me now. Now if only vi had a case-insensitive search. . . .How many times have I done a **grep -i** to find lines that I couldn’t find with vi. . . . . ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 21, 2002, 8:52pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/11 "2002-11-21T20:52:55Z")
> [@](#): > > \*Originally posted by CookingWithGas \* > Anyway, I have always bemoaned case-sensitivity but I’ve used Unix so long I’m sort of used to it and it seems almost normal to me now. Now if only vi had a case-insensitive search. . . .How many times have I done a **grep -i** to find lines that I couldn’t find with vi. . . . . Well, first of all, add the following to your .exrc file set ignorecase And vi will do case insensitive search. RTFM Secondly, in tcsh, I have the following in my .tcshrc (or .cshrc if you go that way): alias igrep “grep -i” which saves some strokes. Neither of which should be related to file system case sensitivity in most situations as this deals with file _contents_. For most file types, case sensitivity in contents is a must. I like using mixed case in file names. E.g., “MyNewProg.c” for readability. (It follows a good variable naming style in programming.) Note: I _never_ use blanks in file names as that is a cardinal sin worth of damnation. Anyway, I want “MyNewProg.c” to be that name under any listing under any format on any machine. Period. BTW, I am really “FtG” but it’s so hopeless getting systems to understand that. Sigh. ---
**Author:** ![John\_T.Conklin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_t.conklin/32/3307_2.png) [@John\_T.Conklin](https://boards.straightdope.com/u/John_T.Conklin)\ **Post date:** [November 21, 2002, 9:37pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/12 "2002-11-21T21:37:42Z")
> [@](#): > > \*Originally posted by erislover \* > \*\*I have never seen capitalization matter whatsoever. But for all I know there might be some crazy email system somewhere that is case sensitive. > > I don’t see anything in the [SMTP](http://www.imc.org/rfc1869) which requires case-insensitive treatment, nor in [POP3](http://www.faqs.org/rfcs/rfc1081.html). So, I suppose it is possible. \*\* [RFC822: Standard for the Format of ARPA Internet Text Messages](http://www.faqs.org/rfcs/rfc822.html). Section 6, Address Specification, shows that the local part (ie. the portion of the address before the ‘@’) must be uninterpreted and case preserved. However, there is nothing to suggest that the destination Mail Transfer Agent can’t fold case when converting the local part to a mailbox. The BSD mailaddr(7) man page (although non-normative, it’s not written in standardese) states: > [@](#): > > Domain names (i.e., anything after the ‘@’ sign) may be given in any mixture of upper and lower case. Most hosts accept any combination of case in user names, although there are exceptions. So while it is probably true that you can use any case in an email address, you can’t assume this will be so in the general case. ---
**Author:** ![erislover](https://avatars.discourse-cdn.com/v4/letter/e/71e660/32.png) [@erislover](https://boards.straightdope.com/u/erislover)\ **Post date:** [November 26, 2002, 7:05pm UTC](https://boards.straightdope.com/t/does-capitalization-in-e-mail-addresses-matter-at-all/137961/13 "2002-11-26T19:05:04Z")
Thank you, **John T. Conklin.** That was what I suspected.