Does posting a letter create any 'legal' agreement between myself and
the postal service? Is there any obligation to deliver a letter?
Assuming that an agreement is formed, at what point in the process?
When the letter entered a post-box, when it was picked up from the
postbox, or later - perhaps when a post-mark is added by the postal
service?
Posting a letter in Germany does not create a contractual agreement between you and the postal service (and so your follow up question above does not apply).
Instead, German postal service activities are governed by the Postal Act and regulations adopted by the postal service. The Postal Act creates a system in which independent contractors licensed by the government carry out parts of the process of delivering the mail and are given quasi-governmental status in connection with these activities. Since it is quasi-governmental it has immunity from legal liability, except as set forth expressly by statute.
The postal service and its contractors and employees are required to follow the Postal Act and related regulations, and the people and entities involved in doing so may have legal liability for compensatory damages caused to someone as a result of their intentional or negligent violation of the regulations. In contrast, contactual liability is generally imposed without regard to fault and any failure to perform as expected by the parties is actionable.
So, in Germany, you can't prevail in suing the postal service or a contractor or postal employee simply by showing that a letter wasn't delivered in a timely fashion, or wasn't forwarded appropriately. You also have to show a court why this happened and demonstrate that the conduct that caused this to happen was intentional or negligent compared to the standard of care for postal workers in the situation in which the alleged misconduct occurred.
German law, generally speaking, interprets compensatory damages rather narrowly compared to U.S. courts, for example, generally excluding damages for inconvenience and emotional distress, and favors orders compelling someone to carry out a duty in lieu of a damages award for failure to perform a duty, when possible.
Some of the obligations of contractors and employees, such as delivery deadlines, are overall performance standards which are not enforceable in individual cases because not every letter must meet those standards, only a certain percentage of a letters in the system.
What commitments beyond the happy-path described above exist? Is there
any commitment to attempt to deliver a letter with a less than perfect
address (e.g. missing out the postal-code)? Or to offer the recipient
the chance to pay the additional postage owed on a letter without
enough postage?
The highlighted language in subparagraph 4 of the portion of the Postal Universal Service Ordinance quoted at length below governs what should be done in this situation. (There may be additional requirements set forth in other regulations or in individual subcontractor license agreements; this answer is not comprehensive.)
The pertinent provisions of the Postal Act provide that:
Chapter VII Service of Documents under Public Law Regulations
§33 Service of Documents Requirement
(1) Any licensee providing letter post delivery services shall
undertake to serve documents, irrespective of their weight, in
accordance with the provisions of the relevant rules of procedure and
legislation on the rules of service in administrative procedure.
Sovereign powers commensurate with this obligation shall be vested in
the licensee (entrepreneur charged with specific functions in the
public interest).
(2) The Regulatory Authority shall exempt from the obligation
according to (1) above a licensee thus obliged, upon its request,
provided the licensee does not have a dominant position in the market.
Exemption is ruled out if there is reason to believe that service of
documents according to (1) above would no longer be ensured across the
Federal Republic of Germany as a result. Exemption may be revoked if
the licensee becomes dominant in the market or if the condition set
forth in sentence 2 above becomes applicable. A request for exemption
may be linked to an application for licence grant.
§35 Liability in the Performance of Service of Documents
Liable for any damage caused by neglect of duty in the performance of
service of documents shall be the licensee obliged, in accordance with
the regulations governing a civil service employer’s liability for
damages in the territorial area. . . .
§38 Liability for Damages
Whosoever intentionally or negligently violates this Act, an ordinance
having the force of law issued by virtue of this Act, any obligation
arising from a licence or any other Regulatory Authority order shall,
to the extent that the legal provision, obligation or order aims to
protect another party, be obliged to compensate that party for any
damage arising from such violation.
So, the postal service's obligations with regard to delivering mail are a matter of postal service regulations rather than being in the nature of contracts. And, if an employee or contractor of the postal service causes harm by intentionally or negligently disregarding the regulations, that employee or contractor is obligated to pay compensatory damages to someone harmed by that violation.
The primary postal service regulation in Germany, is called the Postal Universal Service Ordinance. Some pertinent provisions of this regulation state:
There shall be sufficient letter boxes that customers in urban areas will not need, as a rule, to travel more than 1,000 metres to
reach one. Letter boxes shall be emptied every working day and,
depending on requirements, on Sundays and bank holidays, as frequently
as is needed to comply with the quality standards cited in subpara 3.
Letter box clearances shall be based on the dictates of business life;
clearance times are to be indicated on the letter boxes. Letter boxes
within the meaning of sentences 1 and 2 above may also be other
receptacles that are suitable for posting letters.
Of the inland letter items mailed on a working day, at least 80 per cent on average, over the year, must be delivered on the working day
following the day of mailing and 95 per cent by the second working day
following mailing – with the exception of items subject to the
requirement of a minimum 50 items per mailing. In respect of
intra-Community cross-border mail the quality standards laid down in
the Annex to Directive 97/67/EC of the European Parliament and of the
Council of 15 December 1997 on common rules for the development of the
internal market of Community postal services and the improvement of
quality of service (OJ 1998 No. L 15/14) shall apply. If the Annex to
the Directive is amended the quality standards in the amended version
shall apply as from the first day of the third month following
publication of the amendment.
Letter items shall be delivered, unless the addressee – by establishing a PO box or in any other way – has declared that he
intends to collect the items. Delivery shall be made to the residence
or business premises stated in the address, by placing the items in a
receptacle specifically for the addressee and large enough to be
provided with the items, or by handing the items over in person. Any
items that cannot be delivered in accordance with sentence 2 shall be
handed over to an alternative recipient, where possible, unless there
are instructions to the contrary from the sender or addressee. Where
the addressee’s residential or business address can only be reached
with undue difficulty or in the absence of a suitable or accessible
receptacle for the letter items, the addressee may be excluded from
delivery. The person so affected shall be informed of this intended
exclusion.
There shall be a minimum of one delivery per working day.
The structure of postal service law in Germany, as a question of administrative law regarding the functioning of a government agency, rather than as a contract between the person sending a letter than the postal service, would be typical of most countries (although in many countries there would not be the added complication of providing postal services through independent contractors).