Looking through the 4E rulebooks for commcode examples and MSP names, but not finding much of anything. Does anyone know if there is an "official" take on this?

I'm trying to figure out how the header information for message exchanges between commlinks would look.

I'd just go with what they have in 3rd ed. Take a look through some of the old adventures and there are examples in them.

In 2E/3E, commcodes were more synonymous with what we would think of as phone numbers. The LTG was a four-digit component roughly analogous to our current-day area codes. The rest of the code was six digits, for a total of a 10-digit code.

Obviously a 10-digit code is grossly insufficient for the needs of a wireless Matrix as introduced in 4E. I can't think of any concrete examples off the top of my head that I can point you too, but I vaguely recall the commcodes being fully alpha-numeric. If so, and if commcodes are still 10 characters, that would increase the number of available commcodes to 3.66 quadrillion (3.656 * 10^15). That seems sufficient, as that's roughly 500,000 for each person on Earth. (I know they're not assigned individually, but that still seems like enough to represent everything Wireless-enabled that a person would come into contact with.)

Or someone who actually knows the answer can call BS and point us in the right direction. That said, I think any examples will be from fluff/fiction, not from the rules themselves. As such, it may not qualify as "official", depending on your definition.

Taken from the Seattle mission "Hiding In The Dark", the commcode to contact KSAF Editor Athena Tatopoulos is LTG (2176)-12689.

That seems to be it, thanks!

An official commcode is made up of Grid/Local Grid/Local Numer/Identifier Number. For instance the Downtown Seattle YMCA's Commcode is UCAS/SEA/206/52-4985, according to the Seattle Sourcebook and the 1E Core. 206 is private/Downtown (2206 is government or megacorp). 52-4985 is the individual identifier. SEA is the Seattle local grid, and UCAS is the UCAS public grid.

An exterritorial megacorp commcode would probably be Corp Grid/Local Corp Grid/Local Signifier/Identifier. A mobile commcode would likely be Megacorp Affiliate Grid/Provider Grid/Identifier.

Grid Adresses likely double as commcodes. They did in 1E thru 3E, at least, back when world building about the Matrix wasn't "we just make shit up and don't even try to tie it together logically".

if you want to be 80s it will be a phone number
If you want to be 90s it will be an ip4 eg 5.4.9.4
If you want to be 00s it will be a domain name
If you want to be futuristist it will be a thing that is looked up by and machine and can only be decoded by a machine
Or just go with ip6 2001:0db8:85a3:0000:0000:8a2e:0370:7334