Mailing
Ideally your wedding invitations should be sent by post. Even if you are posting to a colleague at work or a next door neighbour….Yes, even your parents should receive an invitation by post.
It’s a good idea to assemble one complete invitation, with any inserts such as guest information, maps, reply cards etc., and take this to the post office to weigh it and check that it will comply with the mail regulations for posting, you don’t want to risk your invitations getting lost in the post. You will then know how much each invitation costs and will be able to ensure the rest of your invitations are stamped correctly.

Timing
If the guests will need to travel a distance to get to your wedding, the more notice you can give them, the better. They may need to organise time off work, arrange a baby sitter, book flights, book a hotel. 10 weeks notice for these guests would be preferable.
For guests who live locally to your wedding venue and wedding reception, 8 weeks notice is fairly usual.

Envelopes – how to word the envelope
According to those in the know, it is preferable to handwrite your envelope, a printed label is just not personal enough. If you do use a label, try and use a font that looks like handwriting! Or use a calligrapher.
You should avoid any abbreviations, especially for street names, cities or states and use the full name of the guest you are inviting on the envelope. For professionals, you should use their titles, but again, not the abbreviated version, Doctor not Dr. and Colonel not Col. On the envelope you shouldn’t include the ‘and guest’, save that for the invitation itself, the same applies for children. You could decide to use and outer and an inner envelope, this means that the outer envelope is addressed to the main member of the household and the inner envelope is addressed more informally to other guests, this can be useful for larger groups of guests and for children. For the more formal invitation, the children are listed in order of their age and anyone over eighteen deserves their own invitation! The etiquette for couples who live together and for same sex couples is that the envelope should be addressed alphabetically by the last name.