The SMS actually says “flight plan filed”. I didn’t know that it meant it was acknowledged. Thank you for the information.
I would say virtually every IFR plan that’s “filed” via programs like aurorouter etc. is “accepted”. If it weren’t “accepted”, it wouldn’t be “filed”. 
2) Because the weather at the destination airport is below CAT I minima.
In this case you have to include your own minimum in the remark field of your FPL if you can perform low visibility operations. If you’re not LVO approved, you cannot depart.
Even if you have two alternatives?
In fact, this does not make sense (which doesn’t mean it doesn’t happen). The destination weather between ATD and ETA can be very different. Often, in winter mornings, one will depart with the destination totally fogged in (at least if the forecast gives a good chance that the fog will lift. Did that several times with no suspension – heaven forbid – taking place whatsoever.
Few comments :
I would say virtually every IFR plan that’s “filed” via programs like aurorouter etc. is “accepted”. If it weren’t “accepted”, it wouldn’t be “filed”.
Not necessarily. I’ve one (1) example with eurofpl where the FPL I filed returned a “MAN” message from IFPS. It was in 2013.
Even if you have two alternatives?
Yes.
In fact, this does not make sense (which doesn’t mean it doesn’t happen). The destination weather between ATD and ETA can be very different. Often, in winter mornings, one will depart with the destination totally fogged in (at least if the forecast gives a good chance that the fog will lift. Did that several times with no suspension – heaven forbid – taking place whatsoever.
Flight suspension due to exceptional condition (XCD) is based on aircraft ETA. ETA is calculated by NM (formerly CFMU) with the filed EOBT, taxi time and flight profile.
That means the flight suspension takes flight time into account (provided the suspension is related to weather at the destination airport).
I’ve one (1) example with eurofpl where the FPL I filed returned a “MAN” message from IFPS.
An example for a manual plan would be POGO plans (between two Paris group airports).
provided the suspension is related to weather at the destination airport
Yeah but fog forecasts are notoriously unreliable
Not necessarily. I’ve one (1) example with eurofpl where the FPL I filed returned a “MAN” message from IFPS. It was in 2013.
autorouter only tells you “successfully filed” when the plan was accepted by Eurocontrol. If the flight plan goes to the manual correction queue, you will be told so and informed about all status updates (accepted/rejected). Besides the POGO case and some exceptional circumstances (bugs in either Eurocontrol NM or our software), plans never go to the manual queue.
autorouter only tells you “successfully filed” when the plan was accepted by Eurocontrol.
Would it make it more clear to phrase the success message “Plan successfully filed and accepted”? That might remove the confusion by just adding a couple of words.
As a more general comment, I think it is dangerous to give the pilot the illusion that a ACK (or MAN) from Eurocontrol means he can just fly somewhere.
In Europe, generally, it does mean that, but not in the UK where there is a second tier in the form of NATS (London Control, Scottish Control) who will throw out the flight plan which they got from Eurocontrol, if it doesn’t mean their criteria, and those criteria are confidential.
For example you can file an IFR route across the UK which busts loads of CAS, at say 2500ft, and you will get an ACK. But NATS will toss it out when they get it from Eurocontrol, so you get airborne and there is no FP in the system (the dep and dest airports only will have a copy). You get similar stuff in Germany where DFS change routes around, though AFAIK they don’t summarily delete FPs.
I have lost count of the sad stories I have heard (sometimes directly on the radio, and those tend to be more desperate) where a pilot thought a flight plan was some kind of clearance to fly, or PPR/PNR notice.
