//Create a string with the text we want to display.
self.ourText = @"This is your variable-length string. Assign it any way you want!";
 
/* This is where we define the ideal font that the Label wants to use.
   Use the font you want to use and the largest font size you want to use. */
UIFont *font = [UIFont fontWithName:@"Marker Felt" size:28];
 
int i;
/* Time to calculate the needed font size.
   This for loop starts at the largest font size, and decreases by two point sizes (i=i-2)
   Until it either hits a size that will fit or hits the minimum size we want to allow (i > 10) */
for(i = 28; i > 10; i=i-2)
{
	// Set the new font size.
	font = [font fontWithSize:i];
	// You can log the size you're trying: NSLog(@"Trying size: %u", i);
 
	/* This step is important: We make a constraint box 
	   using only the fixed WIDTH of the UILabel. The height will
	   be checked later. */ 
	CGSize constraintSize = CGSizeMake(260.0f, MAXFLOAT);
 
	// This step checks how tall the label would be with the desired font.
	CGSize labelSize = [self.ourText sizeWithFont:font constrainedToSize:constraintSize lineBreakMode:UILineBreakModeWordWrap];
 
	/* Here is where you use the height requirement!
	   Set the value in the if statement to the height of your UILabel
	   If the label fits into your required height, it will break the loop
	   and use that font size. */
	if(labelSize.height <= 180.0f)
		break;
}
// You can see what size the function is using by outputting: NSLog(@"Best size is: %u", i);
 
// Set the UILabel's font to the newly adjusted font.
msg.font = font;
 
// Put the text into the UILabel outlet variable.
msg.text = self.ourText;

<a href="sms:">Opens SMS Application</a>
<a href="sms:1-800-555-1234">Opens New SMS Message to 1-800-555-1234</a>

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"sms:1-800-555-1234"]];

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"mailto:test@test.com?subject=Subject%20Line&body=Body%20Text"]];

- (IBAction)sendEmail {
	/* We want to include this variable text within the premade body. 
	   You could replace this variable text with a personalized message from the user or remove it. */
 
	/* First, encode the variable text (in this case, the mission) 
	   NOTE: self.theMission is our NSString object which contain's the unescaped mission text
	   Replace this variable with your own variable (if needed). */
	NSString *encodedMission = [self.theMission stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
 
	/* Make a string that contains the first part of the static text.
	   We start off with the mailto:email?subject=subject&body=text format.
	   Stop right where you want to put in the variable's text.
	   ---------
	   To make this part easy, use a free web-based URL encoder like the one at: 
	   http://meyerweb.com/eric/tools/dencoder/
	   ---------
	   Our first half will give us:
	   To:Test@Test.com
	   Subject: Subject Text Here
	   Body: Fellow Ninja -
	   (line break)
	   */
	NSString *firstHalf = @"mailto:Test@Test.com?subject=Subject%20Text%20Here&body=Fellow%20Ninja%20-%0D%0A%0D%0A";
 
	/* And the second half of the email (the post-variable segment)
	   Encoded the same way we did the first half. This string will decode to:
	   (line break)
	   Yours,
	   (line break)
	   Ninja Master 
	   */
	NSString *lastHalf = @"%0D%0A%0D%0AYours%2C%0D%0A%0D%0ANinja%20Master";
 
	/* Now we concatenate the strings. */
	NSString *mailCode = [NSString stringWithFormat:@"%@%@%@", firstHalf, encodedMission, lastHalf];
 
	/* Now it's time to send it! The following code makes the above string into a 
	   URL and opens the URL causing the Mail program to launch with a premade email. */
	[[UIApplication sharedApplication] openURL:[NSURL URLWithString:mailCode]];
}